I have a bunch more experience on my 84" front mount snow blower now. Previously I was running a 74" rear PTO, rear facing blower. Tractor is a Kubota L5740 with 50HP at the PTO.
Don't underestimate the power required to blow deeper, heavier snow. Said another way, I think you are underestimating the power needed to blow deeper, heavier snow.
I lost some power switching to a hydraulically powered front blower vs the direct drive rear blower, but the difference in power requirements between 74" and 84" is profound. I could really bog down the engine with the 74", and with the 84" I need to move really slowly. HST or a creaper gear is essential. I run in low range, turtle mode, which for those unfamiliar with Kubotas HST drives, that's the lowest range out of 6 ranges, and then I modulate speed with the HST peddle. When I am clearing snow, the engine is at 100% power the entire time, and I control speed to keep the RPMs us enough to throw the snow far enough. The 84" blower really needs 70-90hp to perform well. It works with 50hp, and I REALLY like having the blower in front vs behind, but it's slow.
In light snow, even deep light snow, it's much less of a problem, but wet snow makes a huge difference. And teh first pass is the slowest because that's when you are taking the full width in one bite. Subsequent passes you can take smaller bites and move faster. For deeper snow falls, you really need to get out and do an intermediate pass before accumulations gets too deep.
So to answer your question, I would lean towards the smaller unit, or be sure you have a really low creeper gear.
I also still struggle with the pull behind blowers. Let's say you successfully drive through 10-12" of snow pulling the blower (I hope you have good chains) and the blower actually cleans down to the road surface. Now it's time for the next, overlapping pass. You have one set of wheels up high going through 10-12" of snow, and the other set of wheels on teh previously cleared surface, so the tractor is tipping to one side. I don't know about you, but my 3PH level follows the tractor's level, so the blower woudl be tilted and I don't think clear down to the road surface across the full width. So how does this work with deeper snow, especially snow that packs hard?