First understand that there's no guaranteeing that an SSRI will be effective for your anxiety. Also, while symptoms may be statistically likely, nothing is typical for an SSRI. There are common side effects, but don't be surprised if you experience something totally different. I was ready to face a host of side effects, but after 2 ssris, by and large I have suffered from none. With that said, I'll try to address each of your qualities with what I know.
1) Weight Gain:
-Celexa is often has more tolerable side effects out of all of the ssris. The most common side effects are weight gain and sexual side effects. With that said, the difference isn't really that significant statistically, and if you are like the majority of people, you will have some sexual side effects and weight gain no matter what ssri you take.
2) Most people can't stop cold turkey. A few can do it no problem. With that said, prozac has the longest half life of any ssri. Your body hangs onto more, for longer. Although I am actually not sure about this, it makes sense to me that the longer half life would have less withdraw effects.
3) Reduce my social anxiety/make me more talkative
- Not sure if one or the other works better at social anxiety reduction
4) Stimulating/Increase motivation
- Prozac is one of the more stimulating ssris. If you're really looking for a motivation increase, I suggest you check out wellbutrin.
5) Least amount of side effects
- Celexa is statistically the most tolerated ssri in terms of side effects.
As far as my own experiences go, I have taken celexa and prozac. Both had little to no noticeable effect on me, good or bad, main or side effect.