I have had both the carb and the EFI.
The EFI is great (when it's tuned) and the carb is good when it's tuned. HA! I have a supercharged LS3 and a factory EFI LS3 and they are great for all of the reasons everybody has stated but, the carb was just about as good for power (maybe better then the factory EFI). I like the idea of not having to use HP tuners to work on my car! I miss the old stuff (big blocks) the LS3 engines will never (to me) replace the old school look and feel of a SBC/BBC. Are they better? I guess thats a question everybody has answer for themselves. I think the LS engines are better for everything except for the cool factor. You will be fine which ever route you go on the induction side of a LS. Both are good.