You can't really go wrong with either of those three. I have ST and MET and AFMr is incoming soon I hope. I can't see any leaving for a long time.
By far the best value is a Met pro... it can definitely be pretty brutal, but it also has a ton of depth to it once your skills improve. If you're looking to "get better" I highly recommend it. Just be prepared for it to kick your butt for a while