Use what works. If the IMR powder is doing the trick for you, why switch? IMR does not meter as well as some other powders through a powder thrower, so if that is a concern...you may want to switch. The dirty part is like has been said before - an extra patch or two. With all of that said, I use many different powders in the fast to medium range some of it has a Hodgdons name on it, but I also use IMR among others. I have been using VV N133 in my 223's with good results, but it is not easy to get. Sinclair International is not too far away from me and that is where I got my last batch. So availability is a factor too.