I generally use && for it (similarly I use || for or), but that's because I come from a C++ background where it's used like that. But there's not too much difference between the two as far as I know, so it's probably just preference. (Edit: except for the priorities as Cozzie says).
I don't know much about RMXP though, only VX, so whether there are any issues that have remained in things like && and 'and' I have no idea.