Well it depends on what your meets your needs. The 2x has a shorter PCB so if length is an issue it may be the better choice. It also requires two 6-pin power connectors vs the 3x which requires 6+8.
In therms of aesthetics I like the 3x a lot more but I would imagine they are very close in terms of performance. Basically I would go for the 3x if it can fit.