Has the MX Master been refreshed at all? The amazon link has user reviews from 2015, and a Google search for "
Logitech MX Master Review" has it listed as the second best mouse for 2017 by TechRadar, posted May 1st.
The G602 is ok, but the center button (scroll wheel click) stops working fairly quickly. This is almost a universal problem. I'm not sure why it's so well-reviewed - it is a great mouse apart from that - but still. People figured out if you take out the batteries and shake the mouse vigorously, it works for a while again, so that's pretty weird. Logitech replaces them I've heard, but people have said the replacements had the same issue, so I never bothered. Upgraded to the G900 and it's great.
For my g703, I contacted them (they apparently share a weakness), and they replaced it fairly quickly -- I think there was a v2 that addressed the issue, a easily broken bit that connected the wheel to the gear.