So you can have sweet-spots in the range where a model represents a perfect balance of price and performance and likewise you can have versions that don't, due to perhaps not fulfilling their original remit correctly.
But what's odd is that those sweetspot models are rarely the big sellers in the range, for whatever reason.
Until that is, you come to this BMW 520d. The best-selling model by far in the BMW 5-Series range, it represents around eight of every 10 Fives leaving showrooms in the UK, which is no small number when you consider that the previous generation car sold a hefty 2.2 million during its seven-year shelf life.
To be fair, we're big fans of this new seventh-generation BMW 5-Series and have been since we took our first drive late last year. Globally it accounts for 25 per cent of all BMW profits and it's as if BMW has willingly ploughed money back into this version to make it even better in almost every area.
That might be expected higher up the range but the irony is that it's probably of most benefit to those buyers - the majority - who are walking out of the showroom with a set of 520d keys in their pocket.
After all, this isn't a car that's wearing a £60,000 or £70,000-plus price tag. Yes it might set you back £39,025 but it's likely to be on a company lease scheme, being chosen by someone just getting on to the 5-Series ladder.
Not that it's exactly a hardship mind you. The 2.0-litre turbo-diesel engine produces 190bhp which is enough to get the 520d from 0 to 60mph in 7.5 seconds and on to a 146mph top speed.
Those are very impressive figures, especially when you consider that it will also return 68.8mpg and 108g/km emissions.
But beyond those figures the 520d's real story comes when you press the start button and set off. Yes it's a diesel and yes this is a mid-sized executive saloon but you can't help but be immediately struck by just how good this BMW is, even within the first 50 yards.
Admittedly there is still a little bit of diesel engine rattle from cold, particularly from the roadside, but that soon dissipates once it's warmed up and you're on the move.
Your first impressions are cemented further when you get out on the road. The engine and automatic gearbox are really well matched in refinement terms. Those 190 horses might not sound a huge amount for such a big car but it performs well and, as those on-paper statistics prove, it's no slouch when you're pressing on.
The only times at which the 5-Series can sometimes feel a little breathless are when accelerating hard down a slip road and even then it's not really that bad.
As with the rest of the new 5-Series range, that extra refinement has had a somewhat detrimental effect on the 520d's position as a driver's car.
It's still good but you certainly feel a step removed from the car at the wheel, compared to what went before.
That said, the excellent ride quality 2.0-litre in 7.5 speed /km and lack of wind and road noise are likely to make that a sacrifice worth making for many.
That comfort is underlined by the excellent quality of the interior.
From the superb build to the TFT screen dials that cleverly highlight your engine revs and speed as you drive while leaving the rest in the shade, it's hard to fault.
On our M Sporttrimmed test car the heavily bolstered seats were very comfortable but the steering wheel rim was slightly over-thick, making it a tad uncomfortable to grip from some angles.
There's no questioning the infotainment system, either, which is easy to use, even on the move, and pretty intuitive. The only downside is the gesture control, borrowed from the larger 7-Series, which enables you to raise or lower the volume on the stereo by circling your finger in front of the screen.
While it might be something to show off to friends, the reality is that turning the knob on the dash or using the steering wheel controls are both far faster and easier to use when driving.
Plus, while we wouldn't normally praise a four-door saloon for its practicality, there's a decent amount of space for adults in the rear seats and the boot is surprisingly large too, going back quite far. It's just a shame that split folding rear seats are an extra option at £335.
Overall though, this version of the 5-Series might not be the fastest or the cleanest (that honour goes to the new 520ed) and it may not grab headlines like an M5 flagship but it is the best-seller and for many drivers this 520d will represent the 5-Series.
For that alone BMW should be very happy. This 520d is one of, if not the, best in the new 5-Series range.
LOGBOOK LOWDOWNPrice: from £39,025
Engine: Turbo-diesel - 2.0-litre
Power: 0 to 60mph in 7.5 seconds, 146mph top speed
Fuel economy: 68.8mpg CO2 emissions: 108g/km
Rivals: Audi A6, Mercedes E-Class
Rating: 9/10 hard
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