well, theres a lot of theories on this topic. some people think you can go longer with synthetic oil than regular oil; i dont. however, you will see longer engine life with the switch to synthetic. some people claim more horsepower and better gas mileage; i think these people ate a bad batch of shrooms. as far as, if one brand is better than another, well, thats your preference really, i mean, personally, i use mobil one. some people like the exotic stuff like amsoil, for example. no matter which you pick, youll be better off with a synthetic than any dino oil. heres one way to pick: what do you usually use for oil?...just use the synthetic that the same company makes; most companies make synthetic oil as well as dino oil.
just so you know, theres also synthetic stuff for trannies and diffs, too. though, after 130k, dont bother switching to synthetic tranny fluid, since your clutches have already absorbed the regular stuff thats been in there for 130k, and you might even see some tranny slippage with synthetic at this point. also, the diffs, IMO, are also a waste, but, as youll see, some people have differing opinions.