Graphics cards 101:
When a graphics card manufacturer (either Nvidia or AMD) design and make a GPU, they release it on a 'reference' graphics card. They also supply the GPU to other companies, such as Asus, EVGA, MSI, Zotac, Sapphire etc.
Each of these companies are free to design their own cards built around the GPU.
They will all be slightly different. For example, some will overclock the GPu for more performance, and most will add their own cooling system and design.
Generally, it is a good idea to chose one of these third-party cards rather than the a reference model, as they are usually better.
That said, you do not currently want to get a 750ti. The new Maxwell 900 series from Nvidia is much better. Go for a 950 or 960...