I found that men's jersey's tend to ride up on me. I try to cut the elastic at the bottom to give me some slack. I agree with assassin, the cut is clearly different. I have a Cannonndale Terra, sleeveless shirt that I love. It's really comfy, and breathes well. It has no elastic at the bottom, so it doens't ride up.
I've never tried the MEC shirts, I checked out the l/s one's yesterday, they seemed ok. Did buy the Women's Samurai short from MEC yesterday, and love them. They are a nice weight mtn bike short, longer leg length, and they really wear well in the saddle. I highly recommend them. I wear their chamois as well, although I do like the fit of the Cannondale seperate as well. Whew! Hope this helps.