I can vouch for both Virtex and Liberty Bit - I've been using both for a couple months now and have deposited and withdrawn bitcoins and CAD with no trouble.
Liberty Bit has much lower fees and better options for deposit and withdraw, but they're also much smaller in terms of volume and mostly a sellers market (most of the filled orders are buy orders, making for higher prices). It also has much lower market depth - so it'll collapse / explode faster than Virtex - this can be a good or bad thing depending on the day and what you're holding.
I would consider STARTING with Liberty Bit because it's easier to deposit funds and the rates are lower. Once you've bought some BTC, move them over to Virtex and holding some funds in both. That's what I do :p
Cheers
Zac