Promoting SFI will better help you attract affiliates as promoting Triple Clicks only gets you PRM. You do not have a direct relationship with your PRM. In fact you are not allowed to contact your PRM, SFI does it for you. TripleClicks members don't need a sponsor like SFI affiliates do. You do get commissions though when your PRM buys from Triple Clicks.
So if you are interested in attracting affiliates promoting SFI is the way to go.