The biggest drawback of a 32-bit application is the memory limit. A 32-bit process can only address a maximum of 4GB of RAM. In Borderlands 2 , this limitation can cause problems during intense firefights or in DLC areas like the Tiny Tina's Assault on Dragon Keep where the particle effects and texture loads are heavy.
If you are a playing the base game + DLCs on a modern PC: borderlands 2 64 bit
The 64-bit client handles Anti-Aliasing differently. The in-game FXAA is blurry. The biggest drawback of a 32-bit application is