SL-C3100/SL-C3200:
Pros: Free CF slot and full-size SD slot, internal HDD (but now comparable with Micro-SD cards in N810), well protected display when closed.
Cons: No internal Wi-Fi, no internal Bluetooth (both needs to be extrernal).
N810:
Pros: 800 pixels horizontally, more memory, camera, Wi-Fi, Bluetooth.
Cons: Much worse keyboard (one row less, when pressin upper row, your fingers touch the top part edge).