aah. I got it. I haven't got a chance to ride gs-150 but as I recalled after yamaha yb-100 I bought RP and my observations were as following.
1) seat height is good. good for taller guys.
2) seat was also comfortable.
3) seat was inclined that I was not used to. For the first month I always got slipped to the front whenever I applied brakes.
The only way to adjust is to put more pressure on the handlebar and your chest part while riding and when applying brakes.
I think in newer models there is clip-on bar, that will worsen the situation and riding posture.
4) Shocks absorbers were not that good so the suspension bounced back on every jump.
5) As there are complains for pillion rider, there are more chances of pillion rider falling on you while braking but the seat is also comfortable for pillion rider. My wife had no complaints at all on RP while she always complained about yb-100 and now of cg-125.
6) I also felt less fatigued on RP.
7) About ground clearance and touching on bumps, I don't recall facing any such issues even with pillion riding.
I haven't used gs-150 but my observations are:
1) Good/strong shock absorbers as compared to RP.
2) It has low seat and low riding position (bad point as not comfortable for tall guys)
3) It also seems to push the rider forward while braking. I have seen many riders and it seems they they are glued to fuel tank.
4) It has good weight that supports on bumps and aids stability.
If only seating posture is my priority, I will go like this:
1) Deluxe-125 or cd-100.
I personally feel that cd-100 offers best seating posture as it also has soft springs and good shocks that helps in bumps. I like deluxe because of it has tallest flat seat and very good rectangular swing arm on which any kind of shocks can be installed afterwards.