i guess that really depends how dedicated you are to certain projects. i participated in Correlizer for a short while myself, but only to participate in the Correlizer race that went down not too long ago. if you don't want to completely give up on CPU computing, then perhaps you should load BOINC on your work machines and run Correlizer on those.
as for GPU compute, is there any particular reason you want to put all (or most) of your GPUs on POEM@Home? i recently joined POEM@Home myself for a few reasons - 1) i wanted to start contributing to a life science, 2) it allows my GPU to run relatively cool, and 3) the PPD isn't bad. i'd have them both on Milkyway@Home, except that produces too much heat for my liking right now...so MW@H and POEM it is.
if you don't have any hardware or software limitations, it should just come down to whatever you think is the most important way to contribute to science and society. personally, i'd scrap Collatz, keep Milkyway@Home, and add POEM@Home. while Collatz has its scientific merit, searching for ever larger prime numbers is only so useful from a scientific standpoint, and i feel that the other 2 projects have a much better chance of contributing something significant to the scientific community. i only do Collatz when the MW@H project goes down.