Zero-turn is cooler in the summer because you're sitting in front of the engine, "fleeing" from the heat it disperses as you ride. Ifn your in humid/hot weather state, that could be something to consider.
Zero-turns take a little longer to learn to drive but it's nothing that can't be learned on the first ride, though to cut or drive precisely will take a few hours' seat time and a light touch. They can cut in a sharp "no-radius" U-turn though the pivoting wheel might tear up some grass; I never cared on 5 acres of country lawn.
(A lot of the possible time saved will depend on how many trees and other obstacles you have to cut around.) A conventional mower with engine in front and single rear-wheel drive will take maybe about 20% - 33% longer than a zero-turn to cut the same area. For a one-acre parcel that may not matter much, but still, it adds time to the chore. I used to have a 48" Craftsman front-engine; it would cut 5 acres in 4hr 30min. Then I bought a 60" zero-turn; it did the same acreage in 2'10". Figuring at least 20% of the save time was because of the larger deck--that means that 80% of the time saved (140 minutes)-- or 1 hr 50 minutes was saved each time because the zero-turn was more efficient. Actually, the math works out to 270 minutes vs. 110 minutes, 40% seat time with a zero turn--that's a lot of gas and wear and tear saved over the lifetime of the mower.
Lastly, whatever you buy, if you set up your mower with "Gator Blades" (a mulching blade) you can chop the grass (and leaves) back into the lawn and you'll never have to rake again.
I'd also suggest you try to find a used mower. "Old" doesn't mean 'beat to hell' if you find one that has been well-cared for. The more recent builds have a terrible reputation, mostly deserved because they're Made in China--MTD, Club Cadet, John Deere, et al from Lowe's/Home Depot. Find something built about 15-25 years old that's being sold by a lawn/tractor repair business. They take in used equipment all the time. The older ones will generally have been built with better QC standards.
Gravely, Scag, Kubota, Exmark, Husqvarna are the dependable OEMs. Whatever you choose, front engine or zero-turn, stick with "Non-Lowes (and Home Depot) brands" that are sold at lawn-maintenance supply stores. They'll have better quality merchandise--but be prepared... the prices will make you cry; and wonder if your options are as big as your wishes. I'm a REAL cheep Scrooge mofo--it broke my heart to spend $7Gs for a lawnmower--to do "chores", but that zero-turn was 5x the mower the Craftsman was (and the Craftsman was $3300 when I bought it new). It lasted 5 years and was beat to hell cutting at least 30x per year. It rattled like half a can of marbles and took 4 passes to cut around a tree. I just wish I'da believed my country cousin's advice when he told me that I'd spend at least $1,500 per acre for a used mower if I bought wisely and correctly the first time, with a goal of buy once, cry once. He was right...
If your acre is flat unobstructed open ground, you might get by on the cheap with a Lowes/HD product. Otherwise, I'll stand by my recommendation. By the way, for an acre, you don't need a big deck. 48" is prolly 'too big'--you'll be paying for more than you need; 36" might be on the small side, but 42" sounds like it'd do well. Ask a pro tractor guy what size they'd recommend.
