Ah, the old lig question; I believe sound differences to be not that great, but the psychology of what you are using definitely plays a part. Personally, I like my Rovner, but the BG works just fine for me, I just don't like the over-chunkiness of it somehow, and I feel like it's gonna get in the way so I may be making small unconscious changes to my embouchure. No doubt if I used a BG exclusively I'd get used to it, but I also find the Rovner easier to line up as my BG has all those rubber ridges on it and it's fiddly to get them even at either side of the reed.
The main reason I don't use the 2-screw metal ones is that I feel I may damage the reed, but again this is probably just an unreasonable prejudice; however, if you want to spend 70-odd quid on a Vandoren Optimum lig, it comes with three interchangeable plates where varying amounts of said plates actually touch the reed.
The biggest differences in sound, to my ears anyway, come from how far back along the bark part of the reed you place the lig, and how much you tighten it.
Cheers, Bob