My point is that as it's closed source, we still don't know whether it sends the key to MS anyway (even if the user asks not to link it to their hotmail account). Given MS' complicity in PRISM, it's not a leap of trust I'm willing to make.
Truecrypt has been around for a decade, and only now is someone getting around to doing a real audit. The people behind Truecrypt are completely unknown, and may well be the NSA for all we know. So do you trust them?
That's a fairly trivial check to make. I would be fairly shocked to find out that people have discovered multiple sidechannel attacks against Bitlocker to leak keys out (if you have physical access to the machine while the disk is decrypted), and didn't manage to catch the fact that the key was getting sent over the network.
The more plausible potential for Bitlocker being broken is that there is some subtle flaw in their crypto implementation.
