I have Hunter on my team, but I'm generally a believer that you sit breakout candidates until their breakout is a well established fact, even if it means missing a few big games. Hunter may not break out at all this year, and if he does, it might not be until the end of the season. I generally believe in waiting until it's a sure thing, but that's also because my rosters tend to be insanely loaded at WR/RB.
I can see the temptation to capitalize on Dallas' defense. Vjax is a "fantasy whack-a-mole" and Tampa's pass offense is out of sorts. Both are risks.
Ideally, I wouldn't start either of these guys, but I'd feel just a little better about Vincent Jackson just because he's proven, and because McCown's suckitude in week 1 can be excused away (Carolina has an awesome defense).
It's really close though. If your gut feel likes Hunter more, go with Hunter.