good looks are a subjective matter. everyone will give you their own opinion on what looks good. in fact when they should be telling you that beauty lies in the eye of the beholder i.e. ap ko jo khoobsurat lagay wohi pasand kariay ga.
For me the GS150 has a real macho shape. It's basic, but nicely done. It's very comfortable as well especially the relaxed handle bars. One thing to note is that it's a heavy(weight wise) motorcycle so navigating in tight traffic spaces can become cumbersome. And you'll find small quality niggles here and there.
Piaggio obviously looks more modern. And it looks good as well. Comfort ka if people's word is to be trusted here on Pakwheels then it's very comfortable and a good touring companion.
Again, bikes pehle test drive kar lain to behtar hai. Logon ki baton main a kar decision liya to you might regret it