To be honest with you, I've never really tried what FTRP has to offer.
I've never tried QZRP, hell, I don't even know what it is to be honest.
But what I do know is HL2RP is a damn well near passion to me, I love it... Hyped up as shit for it too.
There is no reason not to try both, even when I was staff on HL2 I still always had time for FT. From my experience in LP HL2 was always more focused on slow passive roleplay most of the time where as FT/QZ had more actions involved and I've always liked both game modes.