I have to say I don't understand why Mercatox gets such animosity. I've traded large volumes on there over a couple of weeks and I didn't have any issues.

BTC deposits were super fast, but I think the source of a lot of the complaints must be XRB deposits and withdrawals. They process them manually, so it can take up to 12 hours.

Other than that, they are perfectly safe to use and currently have the highest volumes so unless you need your transaction processed instantly, there's no reason not to use them.

No reason for these two exchanges to fight either because RaiBlocks will most likely be added to Bittrex soon and then the arbitrage opportunities start because it will be a three way between the XRB exchanges