Hi,
Only thing I would point out is to make two groups in your Update Manager, so you can assign updates like the HP ESXi bundle to the HP blades, and the (presumably) Dell equivalent to Dell servers.
There are not 10G vs 1G issues that I can see. vmotion problems will be all addressed by EVC if configured appropriately. If the CPUs are compatible, this may not even matter.
Note you can just as easily get CPU incompatabilities just by buying two slightly different models of the same blade.I have two identical BL460 G6's that I can't vMotion between at the moment because I only turned on the Executable Memory Protection on one blade's BIOS 