The different GTX 780 are from different manufactures. What happens is NVIDIA releases the GPU and architecture, and it is up to the individual distribution companies to create the card as well as the cooling solution. The card will work fine, and it's near the top specs for it's given price range. If you are looking to use this for video editing/compression or another GPU intensive go with the higher OC or TI models, which will save you processing time. Or...
If you are using this card for high end video gaming, go with the lower level cards as even the stock GTX 780 is overkill for 99.99 of the games out there.
Gigabyte, EVGA, GeForce and PNY are all good choices for card manufactures.
That being said, they are not all equal, try to find the fastest speed you can get for the price when comparing them.