It really depends on what you want to achieve. Personally, I'm focused at the moment to attract as many PSAsas possible, so I'm using sfi4 gateway, because I think the page is realy compact, clean and sums up the idea of SFI AND Tripleclicks perfectly. That page would definitly convince me to join SFI, so I'm led by that logic.
Other than that, I sometimes use Tripleclicks gateway on placec where I believe it'll have effect.
