P67 is for serious games, H67 for peeps who don't need a gfx card
http://goarticles.com/article/P67-Versus-H67-Motherboard-Chipsets/4082334/
P67:
A P67 motherboard is deigned to allow overclocking on your Sandy Bridge CPU, which is great for anyone wanting a build for gaming, or a workstation since you can push the CPU further, or extend your CPUs lifespan by keeping up with more demanding applications. The Sandy Bridge CPUs however have integrated Intel HD Graphics 2000, and the P67 motherboard chipset does not allow access to its integrated graphics. This should be no problem for anyone who wants to game, since it is probably smarter to purchase a better discrete graphics card.
H67:
An H67 motherboard is designed to utilize Sandy Bridges integrated Intel HD Graphics 2000 (On Intels i5-2300, i5-2400, i5-2500, i7-2600) and Intel HD Graphics 3000 (On Intels i5-2500K, and i7-2600K). If you purchase an H67 chipset motherboard you can essentially ditch purchasing a discrete graphics card if its not needed, which can save some cash. As well, when an H67 motherboard generally includes a couple of display port options including HDMI and DVI ports which do allow multiple display support.