I put matt but I regret, I wish I put gloss.
The Gloss makes a place look so much larger and classier and when clean look excellent. The matt look like some kind of public swimmin area changing room. It does however depend lots on the colour, size and most importantl;y the grouting width and colour. And just for the record, you can get glossy non-slip tiles. Alternatively you can get matt octagonal tiles and just put the little glossy squares in between, just to give it a little shine.