+1 to what Steve said. Stripe is king right now with SAAS projects, and BrainTree is right there with them.
Even if you try to fight the rates battle, that 1/4 point is rarely a true 1/4 point unless you are doing a lot of volume - and then there are the fees that VISA/MC tack on in addition to the per transaction fees. All in all, you'll end up paying a minimum of 2.7-2.9% ANYWAY - and you will have to do more work.
If you REALLY REALLY don't want to use one of the SAAS-friendly two, then integrate with Authorize.NET and find a group that will give you "interchange plus" pricing. The group I work for the B2B services company I own charges interchange + 0.03% I believe. That is pretty fair. Just don't forget that Visa/MC will then assess an additional network access fee.