Lets not forget that Ripple supports a transaction volume many times higher than Bitcoin. And transactions get into the ledger within a few seconds instead of 10 minutes to an hour (or more). Furthermore, the Ripple Consensus Ledger simply *does more*, there are built in order books, pathfinding, and payments allowing users to interact more conveniently with fiat IOUs.
Honestly in a comparison of Bitcoin vs Ripple, all I need to see it the bold/underline above. If Ripple would develop a Wallet/Exchange base worth something, then I can see it replacing Bitcoin in the actual use case scenario. Bitcoin has a huge head-start. It is the "First Love" of many people, including myself to a degree - but honestly, so many of us are just plain pissed/frustrated with Bitcoin. It seems to be a nowhere coin - going nowhere, doing nothing, and competitors springing up all around it. Ripple is perhaps THE best positioned coin to displace it (NOT saying it will) IF IT GETS AN EXCHANGE/WALLET BASE ESTABLISHED.
I realize that isn't looking like the plan at present, but I think that may not be bad, becasue I think they are trying to solidify the banks first. If they do manage that, then launch "public access" - then this could go somewhere fast. But I think we'll see this adoption/realization build up slowly for some more time, then pop. So... not yet.