Moving to a new platform for 11g

I have been asked to research platform possibilities for our future 11g upgrade, and really unsure where to go with it.  So here I am.

I am limited to platforms, IBM and HP.  So the playing field is pretty even, I have experience in both worlds, and as a DBA I haven't seen faults in one that don't exist in the other. 

Here is a little background, we have a 1.2 Tb datawarehouse that processes its loads on a nightly basis in about 5 hours on a HP 74XX partition with 8 CPU's and 6 Gb memory.  We have an OLTP environment of about 300 Gb with batch loads happening in the night, this is the heaviest processing, it is running on a HP 74XX partition with 4 CPU's and 4 Gb memory.