Yes, 195/55R15 will be more comfortable than 195/50R15. 50 series should have slightly stiffer sidewall.Currently I'm using Michelin's PS3 195/50/R15 on my Myvi. I'm currently on GAB's lowering spring with Improve Comfort absorbers. The ride feels ok except for a little bumpiness. I'm now thinking of getting 195/55/R15 on my next change.
It should improve the bumpiness by a little right? Only thing is speedometer will be a little inaccurate and when full load it may scrub?
As for speed reading 195/50 actual reads faster, means if meter shows 100kph, actually you are doing 99kph. For 195/55 will read slower, means meter shows 100, you are doing 102kph. Very small difference to be worried about.
Tyre scrub fender will also depends on your rims offset. If 40 and above should not be a problem, but best is still to test them out first.
However 195/55 tyres are more expensive....