The GTX 480 has a slightly higher clock speed than the Tesla, but half the memory. Buy the Tesla if you need to allocate big blocks of device memory. You can pin host memory to expand the memory pool, but it will always be faster to stay on chip than access across the bus. Also keep the kernel run time limit in mind; the GTX 480 in my system has a limit (as reported by deviceQuery) but my Tesla doesn’t. Heavy scientific computing may also need the better accuracy from memory ECC in the Tesla line. ECC slows things down, of course, but you can always disable it for more speed. The Tesla is more than fast enough for my needs, and the bigger device memory is more suitable for my application. It all comes down to your needs.