I've seen good, bad and in between from all makers of small and large engines that I have experienced through operation and/or ownership. All manufactures have a bad and a "Monday" engine.
The (vertical shaft) Tecumseh 13hp put out in the early/mid 90's and 15hp early 2000's, made for MTD riders, were beasts. On the purchase of both those riders, went out bought the MTD Brigs, brought it home, tried it, took it back and brought the Tecumseh home - it stayed. The Brigs we brought home had no power on the hills, couldn't handle our land.
The Carb is the main issue they have, same with the Brigs, most of that is owner related. People want to put their lawn mower up for the winter without draining the gas out of the bowl, then fire it next season without spraying a little oil in the spark plug hole. Next thing you know they are calling it a POS.