Hi,
Let me give you some perspective on horsepower. I owned a compact utility tractor, that when outfitted to move dirt (front end loader,
ballast in the rear tires and ballast box hanging off the three point hitch) weighed in at over 3500 lbs and would push a 5 foot loader bucket into virgin ground. This machine had a whopping 20hp and it was enough.
The reason lawn tractors have higher horsepower and lower price is cost and target market. Someone shopping for a lawn tractor (lawn mower) isn't expected to know a lot about machines, but everyone understands horsepower. So, you increase what is cheaper (horsepower) and leave out the expensive, non-obvious, stuff (better tranny, stronger frame, stronger deck, ability to really use other attachments well), smart product marketing. Someone who is shopping for a garden tractor is expected to know more about what they are looking for (ability to move some dirt around, use some attachments like snow blowers, blades etc). These people understand that you don't need all that much horsepower (the big old 1940s deeres only had about 14 hp), and that heavy frames, good tranny's etc mean the machine can do more work for a longer time without becoming a scrap heap. So for these folks, the companies put in the expensive stuff and leave out what won't sell (Hp). It's all product marketing.
FWIW, I used to own a 2000 series Cub (2165), 46" deck, triple bagger, hydro. Wonderful machine. The deck and bagger were the easiest to put on/get off of all the machines I've owned (that's 6 now, 2 Cubs, a Craftsman, 2 Deeres and now a BCS). Stay away from the 1000 series machines, they are the result of Cub being bought by MTD.
Mike