Welcome to the team, and great to hear my articles have been useful! =)
You are right that project selection is actually more complex than just picking the lowest number of users:
RAC is a measure of the rate credits are earned. The problem with using this to compare project is that each project sets their own rate at which credits are earned. For example, SETI is notorious for giving out credits significantly more slowly than any other project. I went from 20 million RAC on MooWrapper to 800 thousand RAC on SETI, with the same hardware. Therefore, it is not a very good measure of what project has the best return for your hardware.
The number of users will give you a better idea of competition, but the problem here is that we have no easy way of telling how many of those users are still active 24/7.
Currently, the best GPU project is Enigma. The best CPU project is Yafu.
RE: Hardware and Project Selection Part 2 - GPU Projects