For video editing the X1600 hands down.
playback:
http://www.firingsquad.com/hardware/ati_catalyst_5.13_video_quality/
Encoding is still pretty much immature, but fast, and there will be a new AVIVO update in the Cat 6.4, so who knows what they've added (feature to the X300-850 line or added encoding tweaks?).
For gaming, they will be close enough, but likely the X1600 again, as the direct competition for the GF7400 is the X1400. It is very hard to find comparisons especially for such non-related cards as the GF7400 aand X1400.
Neither is a great gamer but both should give you playable framerates (albeit at lower than native resolution) in any new game for the next year or so. As it gets older you'll have to nudge closer to 800x600 or even 640x480, but at least you'll be able to play.
Of course the Gf7800GO would be a better gamer, different category of chip (competes with Mobile Radeon X1800 not X1600), however for the video editing side the X1600 would still be better. Not that the nV chips are bad, just that with the advantage of AVIVO the X1K series has a current advantage, just like the nV chips had an advantage there for a while with PureVideo before AVIVO came out. Also AVIVO is free so that's a nice bonus.
Overall both will do the basics, gaming will never be their greatest strengths, but the X1600 should let you play what is IMO the toughest game currently out there, Oblivion, @ 1024x768 with everything on (not maxed, but still on).
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