Thanks all for the advice,
I think I'll use caulk to be sure no water gets in there. This moulding was high dollar not to mention the time spent in the prime, sand, prime, sand, paint, sand, paint, sand, paint, sand, paint process
The joint is only a 1/16th so the caulk shouldn't stand out too much.
I'll get some pics posted of the whole project when I'm finished, the countertops aren't the only tile, we used 18x18 Italian porcelean with 1/16 joint on the floor which turned out pretty good for an ametuer tilesetter.