Yeah, the ASUS board was out first and so it's sold a lot more units, which also means it's easier to find forum threads about it (both good and bad ). For the P6N board(s), a good place to start is
here. There is a reference section in the first post of that thread, including links to several other threads, reviews official support pages, etc.
Off-hand, there are some physical and other differences between the MSI P6N SLI-FI and ASUS P5N-E that might be worth noting...
PCI Slots: MSI has
3, ASUS has 2
Audio: MSI has
8 channels, ASUS has 6
LAN: MSI - Realtek RTL8211BL, ASUS - Marvell 88E1116 (~shrug~)
S/PDIF: MSI -
optical only, ASUS -
coaxial only
Cooling: MSI - heatsinks on NB
and SB... ASUS - heatsink on NB only.
eSATA: MSI - none (Platinum version has one)... ASUS -
one, on rear panel
Cost: MSI -
~$113, ASUS - ~$127
...as for overclocking, I've heard it both ways, so it's hard to say which one ultimately overclocks better, but that kinda also depends on what CPU you're planning to use, etc.
For example, the E4300 defaults to 1.8GHz with a 9x multiplier on a 200MHz FSB (800 QDR). If you ramp the FSB up to 400 (1600 QDR), then the cpu will be running at 3.6GHz - a 100% overclock and about all you might expect to get out of that cpu (and I wouldn't advise running at that speed without some better cooling). The forums are full of reports of this board getting 400+ (even 500+) FSB results, so there you go .
The E6300 uses a 7x multiplier, so you have to get the FSB up higher to get the CPU into the 3GHz range. The E6400 uses an 8x multiplier and everything above that CPU uses 9x or more.
For memory... as mentioned, the ASUS has been out longer, so there's a lot more people trying various odd-ball ram in it - making it hard to say if the handfull of folks reporting ram trouble with the MSI P6N equates to the larger sampling of ASUS P5N-E owners reporting ram troubles. The only superficial evidence I've seen one way or the other is a few reports from folks who rma'd thier ASUS board (due to DOA, ram trouble, etc) and were then pleased with thier MSI board, so take that with a grain of salt.
I've been trying to keep a list of "user-reported, working memory" on that link above, so that may be of some help.
Good luck!