With the I5-760 I would opt for the P55A. The only advantage that I'm aware of with the H55/57 MBs is the support for procs with IGP, which the I5-760 does not have. (I3 and I5-6xx clarkdales have IGP, I5-7xx lynnfield do not)
Other than that, look at number Of pci-e x16 and x8 slots - Note any speacial conditions (both have 1 x16 and 1 x16 @x4). also look at Nr usb and Sata connections (h57 7 Sata 3.0, P55A has 8 w two of them @ Sata 6.
My system - I5-750 w/ P55-UD4P (memory Ripjaws 1600, CL7, 1.6 Volts. I choose not to get the "A" version and use a dedicated PCI-e x4 card for USB3 and Sata 6.
Wifes system - I3-540 w/H55 MB (Low voltage G-skill ram, CL 8), The IGP worked fine and is an excellent back-up as I installed a 5670 GPU - (She only plays games that are like $10)