doesn't really matter, you can only gain one stat point every 15 mins (i think its 15) anyway.
i wouldn't do healing simply cos it costs money..if you wanna get your stat point the second the 15 mins is up then i guess a faster re-fire rate skill will be better, but i dont think it matters given the timer. you can do tonnes of skills at once tho if you really want. skill use - item use - swing weapon skill - cast spell, you can gain say arms lore, fencing, tactics, anatomy, musicianship, med, focus, chiv/magery/etc, all at once if you really want. as long as they set to gain at 0.0 and you have no skill points free to actually gain in them, you'll get stats, but there's no need with the timer, one skill will give you gains just as good cos of the 15 min cap. armslore and eval int type skills only have like a 2 second refire tho so i use them. they free too.