A8N-VM boards are a lot smaller n(micro-ATX format) and have fewer open pci slots. They are "value" oriented, don't have northbridge chip fans, etc. They're probably marginally slower and less expandable than the more full featured ASUS mobos. They also have onboard video. These would be perfect for multimedia computers or if you want to build a small/quiet rig, but you're giving up a little bit of speed, some features, and expandability.
The CSM has more SATA ports, firewire and more flexible RAID options. It's probably the "upscale" revision of the mobo chipset and has more features. Dunno if it's any faster though.
Personally I'd get the E or A8N SLI Deluxe. The E doesn't have firewire but if you don't need it, then why pay for it? Plus adding firewire later only requires a fairly cheap upgrade pci card. The one I'd really like is the regular A8N Deluxe. But the only deluxe versions I've seen recently are also SLI. That's not really a bad thing, just probably an unused feature that's all.
