I have the M505 and M705, the ordered and keep both. M505 used my mother on the computer (not just the notebook usable) and the M705 I am Laptop.habe me chose it because of the scrolling function and the additional keys. (I often work with very long texts.)
Compare M505 / M705:
is obvious: both very good, maybe a little Tick m505 front
Press: both also great, even m505 again a little bit better
Scroll: M705 better or lighter than M505
Additional buttons: available in m705, m505 with no
Conclusion: m505 is better in the hand and can be pressed easily, but M705 has additional keys and can be scrolling easier. Have now to what you put more value. I can recommend both.