It isn't really about brand unless you want to pay a bundle of money, it is about what steel alloy has been used, and how accurately the tools have been forged and finished. My system (which is not the only option) is to look only at items that are clearly marked as made from chrome-vanadium steel, and are fairly well finished in the area where it matters: the parts the nut touches. You should take a pocketful of (clean, derusted) nuts and bolts with you, and see if they fit: not loosely, but they will go in under light finger pressure.
If you are going to work on a ride-on today and perhaps a tractor tomorrow, forget about 3/8" drive sets: get half-inch drive. On any tractor bigger than a grey Fergie, you'll need three-quarter inch drive part of the time, but that equipment is far too heavy and clumsy to use for general work.
Having said all that, I still find I'd much rather use a brand-name Australian (Sidchrome), American, Japanese or German tool than anything else. However they would cost twice as much as top-quality Chinese ones, and not function any better. Just watch out for low quality tools, where-ever they are made. If you know a mechanic, discuss it with him or her. Nearly all qualified mechanics know good tools from bad ones.
And the super-short answer is Kincrome is OK in most non-critical applications, but there are plenty of unknown brands at least as good.
