I need to replace the tires on the Camel, and trying to figure out why I should get 215 over 205. Anyone? Please dont say search, Ive done that and I always end up at square 1 - sore eyes and no idea what the eff I just read.

Do 205's have any advantages over 215?

 

While you'd think it was exact (205 and 215 are supposed to refer to mm of width), there are surprisingly large differences in sizes between brands, making a "fat" 205 sometimes wider than a "thin" 215. This makes it impossible, for example, to explain the exact largest size that will fit without rubbing, etc.

Differences in rolling resistance, etc have more to do with the construction of the tire than the size, but if you are looking at different sizes of the same model tire then it is likely the narrower tire would provide slightly (unnoticeably) better gas mileage. Those wide tires are the biggest reason the Mini only has a 1980's style drag coefficient of 0.36.

I'd get the 215s just for better rim protection.

 

One of the reasons why I don't like wide tires and wide wheels is
because i usually end up with tramlining and loose straightline
stability...plus loose the nimbleness as well.

if i had to use wide wheels and tires, i would use a conservative
offset.

 

The answer to 205 vs 215 mm wide tires will depend on your:
Rim size and width
Your intended use
Your budget
Your need for runflats or not
Your need for a large or limited selection of tires of that width

Some things to consider-
Rim size and width-
for 15" rims: 205/50 and 205/55 are very useful tires for performance applications and for street use respectively. 215mm tires are typically skipped over and 225/45 and 225/50 would be next wider but also fit much wider rims better than the stock 15x5.5"
For 16", 17", and 18" rims: you have a choice of sizes but there is more selection typically for 215mm tires than for 205mm tires (true for 17" rims) but it can vary with various sidewall combinations.

Intended use-
Not all possible combinations of sidewall heights and tire widths are available. For street use you can choose from 50 and 55 series tires in 15" and 16" rims that aren't going to fit a MINI if you have 17" or 18" rims. Larger rims usually mean stiffer shorter side walls like 40 or 45 series tires or less. 215mm tires can be found in 35 to 50 series sidewalls depending on rim diameter (not all are practical for the MINI).

Budget-
Some tires in 205 width are going to be less expensive than those in 215mm but it can vary with the various side wall heights that come along with those widths. 205 tires can have a long tread life and can come in all season tires more often.

Runflats-
You'll find more runflats in 195 and 205 widths than you will in 215 widths

Selection of tires-
Really alot of variation with all the combinations out there. Both 205 and 215 will work OK esp for 16" to 18" wheels. You'll get a lighter tire and slightly less rolling resistance with the 205- overall a good street tire that can wear well but that depends on the softness of the rubber compound.
215 tires tend to be more performance oriented, wear faster, be stiffer and harsher riding and sometimes noisier.

About half my wheel sets are 205 and the other half 215. I find both to be OK. I find them to be fairly close for my uses. You can go to the extremes of 225/45 and 175/65 to see how much difference the two can be.