Given the Jazz it's not extra stiff or sporty car, there's really no noticeable difference - from a riding perspective - between 15" and 16" wheels: also the larger ones still carry tyres with a nice and comfy /55 sidewall.
I test drove twice the SR, then bought the EX, the experience with Rome's terrible road condition is more or less the same: Jazz is quite comfy, obviously in comparison to its market segment.