a couple of notes:
first of all, count me among the "do them both" brigade. I usually score the correct one in diagnosis, but not always. Bearings are extremely predictable when built properly, and failure of one is a good sign to just get the other out of the way. There ARE considerable savings in time as it takes a fair bit to set up to do this job properly. Also, for me, this is a time to get everything apart to have a good look around at what state the whole works is in.
Spend the time and money to make proper tools to push on the right parts of the bearing when installing. I usually just turn something on the lathe, but in a pinch, you can take an old bearing and grind the outside to remove a few thou (letting it spin slowly to keep stock removal concentric). You need to be able to push the old one out by the outside race only, and push the new one in by BOTH the inner and outer race at the same time, fully centered (thus easiest to turn a tool to do exactly that).
Make certain that you do everything in the correct order re-assembling - as you can NOT take it off again without destroying the seal (unless the hub is worn to loose fit - in which case you shouldn't be using it anyhow). Please don't embarrass me by asking why I need to remind myself of that.
Again, need a really good puller to get the inner race off of the hub without whacking the crap out of things with a chisel or having puller jaws slip off of race.
Whole thing works best in a properly tooled press
Also, while there is no question Chinese parts COULD be made to Western OEM quality, you really have to have been there to understand how little importance that is within Chinese industrial culture. Results today are all that matter (i.e. the original sale at max profit), not any view towards tomorrow or more so your brand or client's reputation or costs. Truth is, they really can't understand why we care - as it just means more sales to them if they fail sooner. In case I didn't make myself extremely clear: use only FAG, SKF, NTN or other well established brand name parts and if there is a choice, made anywhere BUT China.