#17 has a clean, strong device with great balance in letter thickness and negative space. The swooshes can be diminished or eliminated. I would like to see one symbol with flat color, and one with subtle effect (gradient or glass). The font is so-so; we might try caps letters to the right of M7 device instead of below.
#22 has an interesting merge of the M and 7. If the characters could somehow interact instead of just overlay that would be interesting. I'm going to raise the rank of #22; I like the possibilities.