Xenadrine EFX is pretty weak in my opinion and I haven't rebought a Xenadrine product since they discontinued RFA-1. The other two I don't have personal experience with. Honestly, you are most likely going to be overpaying for an under achieving product when you buy an ephedra free fat burner.

If you still want to take the ephedra free path I would suggest Nutrex's Lipo 6. It has good ingredients and is a major appetite supressor. You will definately be able to see the results if you have never used a fat burner before and it really is one of the few ephedra free ones I would say was worth the money. There are also alot of reviews of people who liked the results they got with Lipo 6, especially if you stack it with ephedrine but you don't have to.