I have been working with the 64 bit version of CamBam for many years. It runs more stable and faster than the 32 bit version. Especially when it comes to memory management, the 64 bit version has an advantage.
Even if you use the 32 bit version with the 4 Gb patch, the calculation of the toolpaths is faster in the 64 bit version.
I often mill 3D reliefs where the calculated toolpaths are in the millions. This takes time, but CB does not crash.