If they both(Gigabyte R9 280x and MSI GTX 770) are available at the same price which one should I get I have also heard that R9 280x has artifacts problem is there any solution to the artifacts problem?
No there are no problems unless you get a defective R9 280X. I have an R9 280X, and I have compared it to a 770. Honestly as much as I like the 1GB extra VRAM for some games, the 770 is just a better card and the NVidia control panel is much easier to deal with.
I now have a 780 and like it much more than the 280X.
Artifacts are caused by faulty cards. That can happen to AMD/Nvidia.
Both cards are pretty close to the same performance, with the 280x(7970ghz rebranded) edgeing the GTX770(GTX 680 rebranded) out by a tiny bit in most games. In some games the GTX 770 comes out on top though. Tom's did an article about the 7970ghz(280x) to show the difference drivers made throughout the year. The 7970ghz was faster overall than the GTX 680, and the r9 280x and GTX 770 are really just tweaked rebrands of the previous generation. http://www.tomshardware.com/reviews/radeon-hd-7970-ghz-edition-review-benchmark,3232-19.html