GS150 has much more riding pleasure than Deluxe, feels more balanced at 100Km/h speed and give no vibrations at this speed (OHC Engine). It lacks in brakes and good seat, otherwise it's better ride. So among these two, i would say go with GS. (i have used both).
Deluxe is more suited to work busy people who hardly have anytime to go to service centers except routine tuning, as it is very less likely to give issues compared to competitors. Its agile handling and responsive engine are a plus for local usage. But still on long rides, it has no comparison with GS. It'll vibrate at 100Km/h speed (OHV Engine).
Piaggio is still a mystery for me. I am having the urge to get one and from what i have heard it is also a smooth ride just like GS plus it has more features. But OHV engine label kind of concerns me that it might vibrate at high RPMs just like Deluxe. vickytulla bro, i would like to hear few words from you on this.