O'Contraire Mon Ami,
CitiFX probably has the most liquidity of any of those brokers. Furthermore, they cover US taxpayers, via the FDIC, for $250K. Even for non-US taxpayers, they have more money than....well, they have more than enough....

Incidentally, their MT4 platform is handled by Boston Technologies, and they have had any problems regarding its operation, so you are going to want to get their MT4 demo account and test it for at least a month or so.

So far as FinFX goes, they are unregulated as many have already said. I did check straight with Integral, their liquidity supplier, and asked them directly how they'd rate FinFX, and they gave it a really fantastic reference. In fact this may not make any difference, but I do assume that they, FinFX, wouldn't wish to do anything to jeapordize their connection with Integral. Only a thought...