Interesting perspectives on the small engine debate. My own experiences: Vanguard on my Hustler zero-turn mower was a complete POS from the get go. Engine was actually replaced under warranty - after three starters, countless batteries, valve adjustments, and trips to the dealer in mid season. The replacement just blew a few weeks ago while sitting at idle (and yes, all regular maintenance was up to date, 'cuz with the troubles I've had with this $4k+ mower, I ain't touchin' nuthin'... dealer does everything). Maybe they're the idiots, but either way, the next replacement is gonna be a Kawasaki or Kohler. Great mower - crap engine.
I have two 10 or 11kw gensets with Honda GX620's that are probably about seven+ years old now. One is emergency power for the house, and one for my back yard shop. Both are electric start, and get fired up a few times a year, with occasional 24/7 operation of a few days to a few weeks after a storm. I run Sunoco Supreme whateverthehell they call it with a fuel stabilizer, and while not the same type of use as my my mower, I would say it's life is easily as hard. They have always started and run fine every time.
4" Trash pump w/ Yamaha 12hp, pretty much the same story as the Honda's, but it is picky about having good gas. 5 hp B&S on a commercial lawn edger... even worse than the Vanguard. Absolutely, positively have to run it dry every time and then store it with Mechanic in a Bottle, or equivalent, and even then, fresh plug and many cusses to re-fire. My old Troy Bilt "Horse" tiller is actually an 8 hp (I had to check... thought it was a ten for some reason), and it's been heavily used for several months out of the year for over 20 years, according to the boss, er da wife. Worn out I don't know how many sets of tires, tines, rub blocks, belts and reverse hubs - but using the same gas precautions (Sunoco+ and stabilizer) she starts and runs like a champ all day. Think I rebuilt the carb once or twice, air filter, oil changes... standard fair for that long in use, but always starts and runs smooth, and I do use the crap out'a the thing every year. My 2-man auger has a little Honda on it, and I can't count the abuses this thing has survived, but again... like a Timex.
I buy returns, close-outs and damages from a local liquidator and fix 'em up from time to time, and while the B&S are usually ubiquitous as far as parts are concerned, they always seem to need something. The Honda's, rarely so. I realize this anecdotal crap proves nothing, and as already stated - it's all personal, but I've had great luck/success with the Kohler, Honda, Yamaha, and Kawasaki 4 stroke small engines. Enough so that I don't mind paying more to avoid another B&S.
Getting back to the mills and the issue of mo' bigger is always better, I have and do own quite a few Kubota water cooled diesels (Skid Steer Loaders, Tractors, etc.), and have always found them to be rock solid. Still doing my due diligence on just what I'll be cutting and what if any real market exists in our new area. It seems likely that for the purposes of processing the immediately available wood and sawing up cedar for strip built kayaks, some hard woods for furniture, and some oak for fencing, the little Chi-com machine would be fine. Slow and tedious perhaps, but adequate let's say. Now since more power always appeals to my Tim Allen side, the idea of a fully automated diesel hydro mill and firewood processor is tempting to say the least, as long as I can plan a reasonable path for recovering the bulk of my investment. Obviously a bigger, badder, portable has greater possibilities, I just have to make certain that I don't end up in the trap of so many that seem to think that ya just buy the mill or FWP and the world will beat a path to your door with gobs of cash. A lot of the used units that I've inquired about seem to share that history, especially nowadays.
So, veering OT a little further, how are people making money with these mills... really! The manufacturers are convinced that there are millions of people who would gladly sell the family cow for a sawyer if only there were more of them around, and yet - every old circ saw mill around me is now kaput, so what gives? Do I justify the cost against only that which I know I'll do for myself, or do I put on the rosy red glasses and try to convince the crazy woman that sleeps next to me, with an icepick in her hand, that I'm gonna be the next Weyerehauser...if only I can get that 800 hp hydro mill?