That's a really interesting comparison actually - I agree 100%. Having used RP, EBP and B2Bpay, I'd say that EBP isn't sophisticated but its cheap and fairly efficient once you get used to it. RP was a nice middle ground when I used to use it pre-April AMEX deval. B2Bpay is a bit of a pain, b/c they separately authorise each new biller with the actual biller before approving them to be a biller on their platform, so that can be painful at times, although their site seems more sophisticated in its functionality than either RP or EBP.