If the GT5 Bundle comes with a blue PS3, and is not limited in numbers, then GT5 launch will boost more HW then Reach. Even if it is limited editon,, It's soooo blue!!!!
Seriously, I think both will boost hardware, probably GT5 will boost more consoles since it is the first proper GT, and Reach is the second proper Halo on a current gen.
However it depends on ratings. Halo: Reach ratings to me were lower then expected, and I think those 9.3/9.5 ratings will hurt the games sales (as it's no longer that ubber perfect shooter, still amazing). So if GT5 rating are higher, it should sell better comparitivly. However, I don't know if GT5 will get above 9.6/10 ratings.
Still, there are a few factors that could make Halo push more HW, but I vote GT5.
Wait, nevermind, GT5 will of course get a larger hardware boost. It's releasing in November, basically the highest month in consoles sales (along with december). Duh...
But Kinect Halo > Move GT5.... to be fair.