I would stick to the 5w-30 oil unless its starting to cause you problems and you need a thicker oil, then I'd make the switch to the 10w-30 oil.
There were never really that many true synthetic oils out there at the start, most were just regular mineral oil that were refractioned and refined to collect the polyalphaolifins without all the extra junk that we find in our mineral oil (that could react in the engine and form substances that you don't want in there). The refined oils missing the junk we're able to lubricate better, not react as much with its environment, and also could absorb more harmful substances since you are putting in more oil to do the job instead of oil+junk.
The true synthetics, polyalkyleneglycols are completely synthesized by man and its the best oil out there. I know a few brands carry these true sythetic oil like amsoil and others but I'm not sure which companies they are anymore.
Most oil companies produce almost the same product, its very competitive so they must. If you really want the good stuff look for bottles that say German or European formula, something along those lines. These foreign formula oils still have the good stuff in them, ie: large amounts of phosphorus, which is really good for the life of your engine but bad for the environment so out here in North America there have been regulations to reduce the amount of good stuff in our oils.