I'm not at all convinced about making the general user choose between 32- and 64-bit versions at installation, given that even techies disagree on the relative merits [1]. (Sometimes with themselves [2].)

If the system only supports one or the other, the installer should be able to work that out. If it supports both, the installer should at least give some hints as to what the tradeoffs are.

[1] https://blogs.msdn.microsoft.com/ricom/2015/12/29/revisiting...

[2] https://blogs.msdn.microsoft.com/ricom/2016/01/04/64-bit-vis...