It all depends. The S2 with the new 5.0 OS isn't bad at all. Heck my S1 even works great. The Droid is a great phone too. However, I would never use the keyboard and thus find it useless. I'll probably keep the S1 until a blackberry comes out with a phone running on LTE or a phone like the Droid Eris is running on 2.0 not 1.5.
I love my S1.. with all the latest updates they have finally fixed all the bugs with the phone. It's now alot faster than it was before and the responsiveness is great. I bought the droid the day it came out.. Played with it for a few days and had to go back to the storm. The droid has great features and is an awesome phone. I would maybe get it down the road but lots of my friends have BB's and that makes it so much easier to communicate.