I have 2 printers, and I run 2 instances of Octoprint. Both until an hour ago were on Raspi 2's with the crappy Wifi Dongle. I had one on the opposite side of the house, just because of the shit head neighbor downstairs who complained he could hear the printer overnight, and threw a hissy fit like a little girl, but thats another thing..
Anyways, So ya printer 1, opposide side of the house and I could upload files to it, start prints, etc all normal but man streaming video to monitor prints was a nightmare, it would barely work. I bought a wifi extender thinking it was the wifi, but that didn't fix anything. It must be that dreaded usb wifi dongle, while it works good if you're in the same room as the printer like printer 2, it doesn't work well for opposite side of the house streaming.
So i've had the Raspi 3 since they became available at Microcenter just sitting around, and I tweeted out to Octoprint asking if I could just pull the SD card from the raspi2 and toss it in the raspi3 and if it would just work and to my knowledge they said yep and sure as shit it works flawlessly.
Everything is instant as if it was hard wired to the router, video is not delayed at all, I click home and boom the feed is live as it should be, but was never that good w/ the raspi 2.
If you have one, or if you're going to get octoprint for your printer get a raspi 3.
TLDR: Raspi 3 > Raspi 2 for Octoprint. Get one if you're going this route you will be very happy.