For 21 inch, I am sold on Toro alum deck, front wheel drive. On my third one in 35 years. I don't bag, just mulch. Steel deck Toro too heavy, and not as good on suction and lift.
I like fwd as much easier to steer and turn with light bar pressure down.
My son has lawncare business and hate the very ones I like. If you bag, need rear wheel drive, especially for uphills. Front wheel spin damages the lawns. He thinks RWD turns faster on the corners, even on the flat. I don't like, but maybe just never go the the technique down.
He likes the LawnBoy Gold commercial 2 cycles, 6-6.5 hp. Out of produciton and hard to find. The regular Lawnboy 5 hp are plastic junk for hard use.
Used a Toro personal pace and hated it. Too much effort to keep it going ahead.
For his walker, he uses the Toro 54 inch. Super machine.
ZTR is a Lesco, heavy as a tank, but not using it much anymore. The Toro is faster on most home lawns.
IMO, Toro has the best design decks. They are also designed 30 miles from me, and I've had a job offer there, so have seen the R&D that goes into them.
Fiancee' has a 2 or 3 yr old Craftsman fwd 21 inch. Like most Sears stuff, it is rugged, does the job, reliable, just HEAVY and not at all high performance. A reliable slug, starts well, but heavy, way longer, underpowered, not very ergo designed. I hate it.
kcj