A good video. A note in advance, I have GoW but don't own a PS3, so I can only judge Resistance on this video and so I may be a little bit biased!
Weapons: Both seem to have strong weapons. However GoW's sniper seems like more fun than Resistance's, and the chainsaw wins out for me. Also the characters in GoW seem to have more reaction to the weapons. Shotgun blasts blow people back for example. Resistance just seems to have people falling down unless blown sideways by a grenade. Thanks to the 360's rumble you feel it when you get punched in the face by a locust.
Vehicles: GoW looses here. The junker vehicle section felt a bit weak and pointless imo. Resistance's vehicles seem like fun.
Enemies: Both games seem to fail from what I call Half Life 2 syndrome: there seem to only be a half-dozen different enemies. GoW was a bit of a let down as it seemed to can the battle with that huge gorilla like beast. Boss wise Resistance looks like it has some good boss battles though I don't like the whole 'explode into random gibs' deaths. GoW's bosses die in more interesting ways. However the corpser battle, though it looks cool, was a bit weak. Resistance also falls down here in death physics. Too many enemies with floating legs and arms. GoW's bodies fall properly to the ground, and can even be kicked around.
AI: This is a hard one to judge from the video. All I can say here is that the enemies use of cover and flanking in GoW is very impressive.
Art Direction: Both games have different themes so it is hard to judge them. From a concept point of view, both are great though execution varies- see graphics. GoW slips slightly because it features a 32bit grey colour pallet however it features some very fancy in game cut scenes, whereas the video didn't showcase many of Resistance's so its hard to tell.
Multiplayer. Again hard to compare. Resistance seems to be more of a traditional deathmatch and capture the flag, and features more opponents. GoW features 8 max, but is a much tighter game as far as I can tell. Don't get me wrong, Resistance mp seems good, but from experience GoW deathmatch is the beat mp experience I have had for a long time.
Graphics: From the video GoW looks like the victor. Resistance seems like a very pretty game, but it looks like it received a couple less rounds of polish. GoW sacrifices length for its beauty however. The mine level with its organic feel, the rain soaked level, the final showdown, all beautiful. Resistance seems more firmly located in 'the real world' and has a little more variety, but GoW's environments still look nicer. Character wise Resistance fails because its protagonist is in standard army gear, so fails against the super-soldier look of GoW. Also the level of detail seems lower than GoW. I still can't help see that Resistance looks a little bit washed out, and looks more like lastgen 0.99 rather than nextgen 1.0.
Overall: Both games look very strong. If I had a PS3 I would buy Resistance- however it wouldn't be a 'system-seller' for me. Anyone who has a 360 should buy GoW. If both games came on the same format, I would buy GoW, and get Resistance when it came out on budget.
My 2p.