Same design wheel, different diameter why?

[JB052]

Looking at the sales brochure for my CLK W209, I notice that exactly the same design of wheel (Borbet) is available as either a 16" or 17".
Apart from use of lower profile tyres (55/50 down to 45/40) is there any other reason for the diameter choice?

 

[Petrol Pete]

The way they look perhaps ? or different ratios of diff/transmission on similar cars ?

 

[GP801]

Ours has Saiph alloys. Again 16s were standard. 17s were optional which ours has. However despite the name being the same they are not just larger diameter. The 16s have a lip around the rim which is not present on the 17s.

 

[JB052]

I have done a little more digging, it looks like the CLK Elegance had 9 spoke 16" diameter wheels fitted as standard equipment up to the 280 model which is the engine I have in my car.
CLK 320, 350 and 500 were fitted with the same 9 spoke but 17"diameter wheels, which as they are also a wider rim allows wider lower profile tyre fitment. So presume it's related to safety rather than aesthetics.