I'd said the main advantage of ver 2.1 over ver 1.6 is the multitouch feature.

Especially when you are using the browser this feature really makes your browsing better ; the pinch n zoom function is very smooth and fast. If this is not important to you the ver 1.6 is good enough.

It is the experience of just like driving a car - if you are used to driving a big car eg 2000-2500cc you will never wish to drive a smaller cc say 1300-1600 ( of the same make) . You will still achieve your objective - reaching your destination and possibly same time or slightly longer time on the smaller cc car but the feeling/experience during the journey is different