Mantle isn't going to suddenly come out for every game, just a few. I just watched a video with Tim Sweeney, John Carmack and I think a guy who works on BF4 discussing this topic.
**Mantel dead in water or future?
http://www.youtube.com/watch?v=3RF0zgYFFNk
I suggest you compare BENCHMARKS for the 280x to a card like the MSI GTX770 as that card is about the same price (it's $330).
http://www.newegg.com/Product/Product.aspx?Item=N82E16814127741
If you compare apples-to-apples the MSI OC'd GTX770 beats the MSI OC'd 280X slightly.
Other important details:
a) GTX770 comes with THREE free games ($150 new):
- Batman Arkham Origins
- Spliter Cell Blacklist
- AC4 Black Flag
b) Shadowplay (can record 1080p @60Hz with little/no game performance loss. I tested this.)
c) PHYSX
d) SLI beats Crossfire currently (if you ever add another card)
e) G-SYNC:
This technology which is currently NVidia only (may be licensed) works with new G-Sync monitors (Q1 2014) to solve lag, stutter and screen tearing all at the same time.
*G-Sync is a game changer. It's not a minor thing. The experts are all talking about it and blown away.
The difference in VRAM (3GB vs 2GB) is still not that important.
Summary:
- MSI GTX770 is faster slightly
- G-Sync (me want new monitor.)
- three great games!
- AMD's Mantel isn't going to make much impact in the near future if ever (can provide links)