I don't have the specs with me right now, but this is what I can remember off the top of my head :
Since you want onboard video, let's narrow down the comparision between the C18G-400 and the A7N8X-VM. The two are very similar - They're both micro-ATX boards, they both use the nForce2 chipset, they both have GeForce4 MX onboard video, an 8x AGP slot, 3 PCI slots, 10/100 LAN, 6-channel audio.
The main differences are -
The Krypton board has a 15-pin D-sub game port which the Asus doesn't.
The Krypton has 2 rear USB ports plus headers for 4 more. The Asus mobo has 4 rear USB ports plus headers for 2 more.
The Krypton has 3 RAM slots while the Asus board has 2.
The Krypton mobo can run RAM in dual-channel mode while the Asus board needs to have a separate gfx card installed to do this.
The Krypton mobo has a TV-out header. I'm not 100% sure, but I don't think the Asus board has this feature.
As I said, I'm reciting this from memory, so anyone is welcome to correct me if I got something wrong. Performance-wise, I don't have independent third-party benchmarks, but I expect the scores would be quite close.