A lot of the response to Windows 10 has bordered on hysteria. Really, it has. "OH NOES, TELEMETRY!!!111oneone!" Here are some factors to consider:
1. Much of the data that is sent to Microsoft has been sent for a long time before Windows 10 came along.
2. Much of the data that is sent can be turned off when you install it or after.
3. Much of the data that is sent is not unique to Microsoft. How much data does OS X, Ubuntu, Google Chrome browser, Firefox browser, and other application software send to their vendors? If you're going to be paranoid about data that your machine is sending out, you should be paranoid about ALL vendors, and be regularly monitoring your network traffic to see what is going out.
4. Much of the data that is sent is genuinely useful. For instance preferences that replicate across machines, backups of vital data, data to improve performance, etc.
5. Much of the data that is sent is now also sent by Windows 7 and 8.x. They have supposedly back-ported much of the "telemetry" to those OSes, so you would have to play wack-a-mole with updates on those OSes to prevent it.
6. I feel that there's little data that they send that is not covered by items 1-5. I have yet to see anything truly nefarious that they are supposedly sending, but I could be wrong, of course.
7. You're going to have to upgrade eventually anyway, unless you plan to move away from Windows completely. See item 3.
8. It has a lot of improvements in usability and performance. It's nothing revolutionary, but it does add up to a significantly improved OS experience.
9. It's the current OS version. Running the current version of any software typically comes with a variety of advantages (and sometimes, some disadvantages).
10. It's a free upgrade, for a little while longer. See item 7.
In conclusion, there's very little advantage to staying with Windows 7 or 8.x, unless you have software that doesn't support 10 yet. It's perfectly valid to want to move to another OS altogether, but for your own sake, make your decision based on an objective analysis of the pros and cons, not hysteria.