I've had both & I'd prefer the front mount blower if the higher price is acceptable to you. The 3ph blower does have advantages. It's cheaper, a little easier to attach to the tractor, & you get to keep the FEL on. But I blow snow for 5 or 6 hours at a time & sure do prefer to do it facing forward. I have a scraper blade mounted on the 3ph in Winter & the combo of the 72" front blower & the scraper blade is best, in my opinion. I don't miss the FEL in Winter, but I can see how some folks might.
The most important thing when getting a tractor & 3ph blower is to be sure the tractor has sufficient gearing choices in reverse. If the tractor has a manual transmission with only very limited reverse choices you'll be forced to go a lot slower than you could. My current tractor, a NH TC40D with hydro transmission & the NH 72" 716B front mount blower, gets the job done in half the time it took with my previous rig, a JD 950 with 3ph blower and only two reverse gears-- "Too Fast" & Too Slow"
More horsepower with the NH, true, but the most important difference is the old manual JD tranny with only 2 reverse gear choices forced me to go slower than I could have most of the time.
My advice would be to 1st of all get more horsepower than you think you need & a hydro tranny. If the $$ difference in the front vs rear blowers matters a lot, then go for the 3ph blower. It'll work fine. If you can afford to spend the extra $$ to be a little more comfortable, get the front mounted blower.