Both the 875P and the 865PE chipsets support dual channel DDR 400 and FSB 800. With the 875 you get PAT technology and ECC memory support, unlikely you will ever use either. The 848, is back to single channel memory and lacks a few other things. The 845 (as has been said) is also a very stable board, and pretty guaranteed to work with most everything but lacks the ICH5 controller, which means no SATA or Dual Channel Ram, etc.
There are six versions of the 865. The 865G - integrated graphics, 865PE for FSB 800 - no graphics, and the 865P - no graphics and FSB 400/ 533. All three versions can be specified with an integrated Serial-ATA-RAID via ICH5 Southbridge.
The 875 has only 1 other difference and that is the on-board Intel® PRO/1000 network connection, which is further enhanced by the Communication Streaming Architecture (CSA) bus – a special interface that is free from the bandwidth limitations of PCI and increases networking throughput. With the inclusion of the CSA on the Northbridge, it is theoretically possible for latencies to decrease by relieving the traffic congestion on the Southbridge ICH5 chip that can be caused by the flow through an Ethernet connection. This I doubt you will see as a benifit either.
And actually, the 875 is the older of the 875/865 chips. The 865 and 848 were derivatives of the 875P and are evolving chipset segments targeted for non-workstation environments.
ASUS as well as ABIT and GigaByte all have a good reputation. As for which is better? I don't think there is a simple answer. Clearly ASUS has the market share, but many others are equal.
I've used most brands by now. Always hoping that a clear winner would emerge. This hasn't been the case. Right now, I think the ASUS and ABIT boards are both very good.
My advice is to normally use either the ASUS P4P800-DELUXE or the ABIT AI7 or IS7 for the 865PE chipset and 1394 support because this is what most builders are using. I'd choose the ABIT only because there is a widley supported forum for them on line with heavy traffic, so support is available. Asus has killed their site for a unknown period of time.
If you must choose a 875 board, the ABIT IC7-G MAX2 is pretty good as is the ASUS P4C800-E Deluxe (not the P4C800-E Deluxe - UAY).
I have also used the Gigabyte stuff, and its performed pretty well and usually includes more stuff in the box than does ASUS. However, their updates for drivers can be lacking and sometimes the drivers shipped can be questionable. There's nothing perfect though. For instance, some ASUS boards don't give you the SATA "power" converter required of the drive. A $2 part that will cost you grief if you don't know you need it. They give you the SATA interface cable, but not the power one.
