Growing up (about 20 years ago), we bought rotary push-mowers from Sears that were always Tecumseh engined. We'd put maybe 35 hours a year on them, changing the oil each spring and at the 25 hour mark (we kept track - Dad was an engineer and I am too), and they'd be way down on power and mostly useless in about 4 years. (A lifetime of about 140 operating hours)
About 1995, we bought another Sears rotary push-mower, but this time it had a Briggs engine on it. It gets used a lot less, maybe 10 hours a year, but has held up far better. Sure, it has less hours (about 120 now), but it's managed to maintain power over those hours. Only problem is that this engine's carb is very sensitive to dirt - I've had it apart at least three times. No fuel filter, so dirt goes from the tank to the carb, plugs the float valve, and fuel everywhere. Fixed this problem with an add-on fuel filter.
So, I'm a big fan of Briggs over Tecumseh, with the Sno-King being the exception. We had a 5HP snow blower (Ariens) with a Sno-King. It was hard to start, but ran great! We bought an electric starter for it that ended the hard starting.
Lately I've bought two Honda-knock off Chinese engines. The little 6.5 HP jobbies. One is a Jiang Dong brand and is on a generator set ($200 at Costco - couldn't pass it up). The other is just an engine - one of the bargain sub $100 engines, also from Costco. The Jiang Dong starts easy, runs great, and seems to be holding up. Have about 10 hours total on that genset. Haven't run the other one yet...
later,
b