Exzodian :
Performance per dollar
Cooling
Overclocking
etc.
Website - http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&DEPA=0&Order=BESTMATCH&Description=gtx+970&N=-1&isNodeId=1
The G1 970 has the best cooler of ANY gtx970 on the market, the 3 fans do quite good, and it has a backplate which not only looks MUCH better than bare PCB but also helps passively cool the card by directing air-flow properly etc..
Overclocking wise, the G1 is specifically binned with only the best gpu's that gigabyte gets, so it definitely has headroom; both of my gigabyte G1 gaming GTX970's (i'm doing 2 way sli with them) will overclock to 1,500-1,550mhz each.
Honestly the only 970 that i think is better at anything than the G1 gigabyte is the new EVGA FTW+ that's coming out, the SSC is decent too but i think the FTW+ is the only real competition to the G1. The FTW+ has a higher stock boost clock speed (1,367mhz vs 1,329 on the gigabyte G1) and might possibly overclock a bit better, but the cooling isn't quite as good. I have heard that the FTW+ will come with a backplate as well, so that's good though.
For the tie-breaker, i think it depends on two things,
A) do you plan to move up from the GTX970 to a 980 or 980 ti or whatever later? or do you plan to buy a 2nd 970 for SLI? or just keep the one card?
If you would like to have a GTX980 but can't afford one right now, the EVGA FTW+ is a great card, EVGA has fantastic customer service, they will even offer you a "step up program" where, in 6 months or so when you have more money, you trade your GTX970 to them and pay a little extra, and they will trade you for a brand new GTX980 or 980 ti depending on which one you want.
If you plan to just go with SLI then the G1 and the FTW+ are about equal i'd say, but there's one more thing
B) Do you plan to water cool your graphics card at all in the future? If so then definitely get the Gigabyte G1, it is the only GTX970 that has a nice and long PCB design, which means that the EK waterblock that goes on it for water cooling not only looks infinitely better asthetically (the short PCB on all the other asus, evga, msi etc.. 970's when put in a water cooling block make them look like little kids toy gpu's like a GTX 750 or something.) it also gets cooler temps due to having a better waterblock design for the VRM and some of the power phases etc.. and when water cooled the overclocking capabilities of the G1 skyrocket, making up for the ~40mhz lead the EVGA FTW+ card has at stock speeds.
So, if you like the idea of trading in for a GTX980 in the future get the EVGA FTW+ or SSC, if you plan to water cool your gpu now or in the future get the Gigabyte G1, and if you don't plan to do either of these things it depends on whether you would prefer better cooling and overclocking or better customer service and better stock performance.
You can probably tell which one i preferred by the fact that i have two G1 gigabytes, but honestly after hearing all this scandal about the 3.5gb vram thing on the 970's i kind of wish i went with EVGA since Gigabyte REFUSES to offer refunds on false advertising of the gtx970's memory, rop units, and L2 cache. Whereas with EVGA i could just shell out $200 or so and trade in my 970's for full 4gb gtx980's.