I don't do a reset unless there are problems but I usually wipe the system cache. I don't have Motorola. I have a Nexus 5. I'm just learning about Motorola.
Every other Verizon Android phone I have owned 2 HTC and an LG I had to do a factory restore because of issues mostly terrible battery life or major lag and crashing so I am expecting to do it.
Eliminate all doubt. Factory reset after major updates. Just think... When it rolls out and people start posting their nitpicks or oddities, what will everyone's first response be??
" You should Factory Reset, and see if that works."
I have the Moto X Pure, now running Marshmallow and for the first time I did a reset after the update. I wish I had played about with the phone before hand to see if there were any bugs, but after the reset the phone is brilliant, no lag, no bugs.
I updated my Moto X Pure Edition without performing a FDR. I have not experienced any bugs. My belief is don't fix it if it isn't broken, so I only do FDR if something is broken after an update.
I do, mainly because I want to eliminate the possibility of any problems arising due to a "dirty" install. With an O/S update there's a possibility of issues anyway. When I upgrade Windows on my computers, I always do a clean installation; these phones are computers so I treat them the same way.
I'll always give this advice: Hope for the best, plan for the worst.
Major upgrades have a lot of moving parts, one of which is often the runtime libraries that really run all of Android. When those change, you really run the risk of having some bits on your app cache and data that aren't exactly happy to play in the new sandbox.... and your once well-oiled-machine running phone starts to cough and spit. When that occurs, a FDR usually clears that right quick. But not everyone has such issues.
Still, make preparations... make sure your photos are backed up, go check your backup settings and make sure stuff like your WIFI config, contacts, etc... all are backed up. Plug your phone into a computer and make a backup of your internal storage, etc.... That way if you DO have to do a reset, it's as painless as you can make it.