I usually only do floors,but i suppose the principal is the same,personally,i`d say oil,because it repells liquid(although you do have to refresh it from time to time),i believe they do some sort of anti bacterial one specifically for the job,on a floor i`d usually only go down to a 120 grit,but you may be better going down to 150 on a worktop(just because you see it closer up than a floor),any finer and you close the grain and make it harder for the oil to penetrate,2 possibly 3 thin coats should do it(wipe off any blead out before it dries).
wax may cause water marks
varnish can easily get damaged by knives etc.and is harder to repair.
I may be wrong on some of these points,but i`m sure someone will point them out [smile]