Yes, I've run both. For me, M1A kicks in quicker, but it's mostly glycogen buildup. Msten takes a little longer, but tends to yield higher quality gains. This is just my experience. I like them both. M1A tends to aggravate a small amount of gyno I have developed over time, but it's very minor and a little bit of letro/ralox usually knocks it right out. If this is just a kickstart and you're running it 4 weeks, I'd lean toward Msten, but either should get the job done.