It makes so much difference in that it keeps your front wheel from throwing crud into you drive train which extends the drive train life considerably.

The 3 speed wheels and chain came off my old winter bike after I had ridden them 7000 km... there was no measureable wear on that chain and after another winter where I may have ridden 2000km... the chain still looks and measures out like it was new.

It is not inconceivable that one might get 15,000 - 20,000 km out of a quality chain on a 3 speed if you keep it clean and lubed.