Audi A4 vs BMW 3 Series, Mercedes C-Class and Alfa Romeo Giulia: which should you buy?

The Audi A4, BMW 3 Series, Mercedes C-Class and Alfa Romeo Giulia are four of the most popular and desirable compact executive saloon cars you can buy. These models compete with each other for sales alongside other models such as the Volvo S60 and even the Tesla Model 3.

However, the big four are the big players in this market. They are called compact executive saloons, or compact execs, because they are smaller than traditional executive cars such as the BMW 5 Series or Mercedes E-Class.

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Each of these models offers something a bit different from the other - the BMW is good to drive, the Mercedes is comfortable, the Audi has a great interior and the Alfa has a stylish exterior. These cars are all great all-rounders, though, making it hard to decide which is best. Here we’ll look at the differences between them and find out which one is right for you.

Size and style

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The Audi A4 is perhaps the most conservative model of the lot in terms of design. It’s hardly changed in the years it has been on sale, even across different generations. But that’s not necessarily a bad thing, as its classy and elegant styling is likely to appeal to more than the bold and dramatic looks of some rivals.

The BMW 3 Series and Mercedes C-Class are similar in that they have also gradually evolved over time, each featuring a fairly understated look (aside from the high-performance BMW M3 and Mercedes-AMG C 63 models). There’s a clear stand-out choice in this group if you want something that looks stunning, however - the Alfa Romeo Giulia.

The Italian model is the most interesting and different-looking model and even in basic trim levels it’s more attractive and sporty than even the higher-spec versions of the German cars.

The Audi A4 is 4.8m long and 1.8m wide, so it’s a little longer than its rivals here, which all break the measuring tape at 4.7m-long. The BMW and Mercedes are a similar width, the Alfa Romeo is one of the wider models. It’s only by a matter of millimetres, though - in reality, all these cars are about the same size and will fit into the same size garages and parking spaces easily enough.

The A4 has a roomy interior with a useful 480-litre boot, which is identical to that of the BMW 3 Series and larger than the Mercedes’ 455 litres. The Giulia also has a 480-litre boot, so all three cars are quite practical. The smaller boot in the Mercedes is offset by the fact there’s a bit more room in the back for passengers.

Performance

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The Audi A4 comes with a choice of petrol engines including a 2.0-litre unit with either 148bhp or 201bhp. These are called 35 TFSI and 40 TFSI respectively. Diesel engines are available too and again, it’s a 2.0-litre motor with either 161bhp or 201bhp - or 35 TDI and 40 TDI as they’re badged. All engines in the Audi are punchy and good to drive, since they all have plenty of power. 

The BMW 3 Series range has a similar engine line-up. There’s the 318i, which has 154bhp, then the 320i and 330i variants that have 181bhp and 254bhp respectively. These all use four-cylinder engines, but the M340i is a powerful six-cylinder range-topping version that’s very fast and fun to drive. It rivals the Audi S4, which uses a V6 diesel engine.

The 3 Series comes with 318d, 320d and 330d engines using diesel power. They have plenty of performance but are more economical than the petrol versions. There’s also the 330e, which is a plug-in hybrid. It’s a close rival for the Mercedes C 300 e, which is also a plug-in, and both models are fast and powerful but can also use electric power for fuel-saving drives.

The Mercedes C-Class has C 180 and C2 00 petrol versions, which use a 1.5-litre petrol engine. They have 168bhp and 204bhp respectively and so are a match for the 2.0-litre units in its rivals, plus there’s a 2.0-litre engine in the C 300 model that has 255bhp.

Diesel options in the C-Class include the C 220d and C 300d, which both use 2.0-litre engines. They have 197bhp and 261bhp respectively, so they are both quite powerful, yet still economical.

The Alfa Romeo Giulia comes with 2.0-litre petrol engines with 197bhp and 276bhp. Both are excellent, offering plenty of performance and a fun driving experience, but they have quite a thirst for fuel. There was also a 2.2-litre diesel with 158bhp or 187bhp, which is also punchy and enjoyable to use.

All four models are available in a high-performance version as well. There’s the Audi RS4, BMW M3, Mercedes-AMG C63 and Alfa Romeo Giulia Quadrifoglio. All of these models bring the performance and handling of a true sports car without sacrificing much, if any, practicality. The Audi is only available in Avant estate guise, while Alfa is exclusively a four-door saloon. There’s more choice with the M3, which can be had as a saloon or coupe (badged an M4), plus there’s now an M3 Touring estate. The Mercedes offers the most choice, with saloon, estate, coupe and convertible options.

Efficiency

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For company-car drivers, the best version of any car to choose is a plug-in hybrid. The BMW 330e and Mercedes C 300 e are your choices if you need that, and both can drive on electric power alone for short trips - the Mercedes capable of over 60 miles, which places it in the lowest Benefit-in-Kind bracket.

If you can’t plug in at home, though, a diesel version is a better choice. All four models are available with diesel power, so there’s plenty of choice there. The Audi A4 returns up to 59mpg in 35 TDI form, or there’s the 40 TDI which does about 53mpg. Petrol versions will manage around 45mpg.

The BMW 318d and 320d models return over 61mpg according to official figures, plus the more powerful 330d manages around 53mpg, so we rate the 3 Series range highly for efficiency. The petrol versions will return over 40mpg on paper, but we found that they’re a bit less efficient than that in the real world, with 40mpg being at the high end of realistic.

The C-Class diesel range is good, too. The C220d returns over 61mpg, while the C300d can reach 55mpg. The C200 petrol drops to 44mpg and the C300 petrol dips even further to 42mpg, though they’re also likely to be thirstier than expected. For both the 3 Series and C-Class, the plug-in model makes a lot of sense if you want petrol power.

The Alfa Romeo Giulia has an excellent engine range but it’s not very efficient. The 2.0-litre petrol engine returns 39mpg no matter whether you pick the 197bhp or 276bhp versions, while the now-discontinued 2.2-litre diesel can only manage around 54mpg even in its most economical form. 

Verdict - which should you buy?

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All of these compact executive saloon cars are great options for someone looking for a practical family car that’s enjoyable to drive, doesn’t cost too much to run and has a classy image. 

However, they all have their own style, and which one is best for you depends on what you look for in a car. If you want something that’s comfortable but fun to drive, the BMW 3 Series is the best one to go for - it drives brilliantly and is really comfortable.

The Mercedes C-Class makes more sense if you don’t mind losing a bit of driving enjoyment and gaining a bit more comfort and interior quality. It’s luxurious and easy to drive, plus it’s economical and roomy in the cabin.

The Audi A4 is a sensible choice and has a very high-quality interior packed with technology. It’s not as fun to drive as the BMW or Alfa Romeo, but it’s easy to live with and very practical.

The Alfa Romeo Giulia is a bit of a left-field choice, but don’t discount it - it’s just as sharp to drive than the BMW and equally comfortable. It’s a fantastic car for keen drivers, but it’s not as well made as the others and the interior lacks a little in upmarket appeal, especially when it comes to tech.

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