re your observation, "...It seems the 205s ride is a touch smoother but the 195s ride fine and seem to last longer...," there's a lot more to consider than just size.

Different tire makes and models* differ considerably in their wear, ride comfort, noise, and handling characteristics. The only way you could make even a modicum of generalization like that is by using exactly the same make and model tire, and in exactly the same aspect ratio. But you didn't mention that you did that among your experiences with the two different sizes.

[ * some manufacturers even go so far as to give the same model name to altogether different tires (i.e., different rubber compound, carcass ply material, etc.), one sold in name brand dealers and the other sold in "cut rate" stores like WalMart because they need to be made at different price points.]

On the other hand, years ago when I had Volvos without ABS (I have two '93 240's now), I used to put larger tires in the rear of my wagons to (1) compensate for the towing, and occasional loads in the back that I carried; (2) ensure that the rear had somewhat more traction when braking (I didn't want to rely on the pressure limiters -- those things bolted on the rear axle) so that my fronts would always lock up before the rears (added benefit: good, safe understeer); and (3) like you, I liked the look of the slight rake between front and rear.