In this day and age, you risk lots when you choose to upgrade.
you must ask yourself: is it broken? If it's not broken, why should I fix it?
You should also ask yourself: how long before I get a new phone? If you like to get new phones often, just go out and buy a phone that came with MM from the factory. Or wait until LG comes out with the successor to the V10, which shouldn't be too long, and that will have Android 6 or maybe even Android 7 on it.
If you tend to keep your phone a longer time, roll those dice and upgrade the software. But do be aware, you might see issues. Reported issues are bad battery life and bluetooth issues, among others. Be prepared to solve the bad battery life by doing a factory restore. Before you do that, do a backup to your computer using LG Bridge. Pain, but worth it.
Benefits are newer security updates and overall the fingerprint scanner works better, and is now integrated with the OS for non-LG uses.