if the engine's in good condition, it shouldn't make much of a difference, except to your wallet.
if your engine is leaking or weeping oil anywhere, though, you may want to stick to mineral as those fully synthetic formulations could aggravate the problem. ditto for engines that burn/consume oil.
i suggest go mineral na lang... it's cheap and plentiful, kahit magpalit ka every other month pwede. cost? pareho lang. 875 ang changeoil package sa honda casa, mineral. do it every 6 months in a year 1750 lang (ganito gawain ko). cheapest fully synthetic package i can find is speedyfix's motul * 2,000 all in. you can run that oil for 1 year. so, go figure...
i'm not a fan of shell oils. mahal, despite the fact na napakarami sa market (premium pricing). mas mahal pa nga shell kesa mobil minsan eh. sa mobil nako, may f1 history pa going further back than shell.