You should go with the 60". Your tractor is about 53.5 inches wide at the rear tires. The 51 won't be wide enough. As long as you have an HST with a live PTO, you'll be able to slow the tractor down and keep the blower going to let the tractor catch up, if you get into anything too heavy.
I have a 64" Puma, and my tractor (also a 2015) runs it fairly well. I don't have a live PTO like you, since mine's gear drive, so I have to take smaller bites when the snow is really heavy, or deep. The 54" Puma would've been better for me, but I got a deal I couldn't refuse.
Can't comment on the Meteor brand, since I never used one, but I do see alot of them around.