Factors which would be considered:
1) Deck penetration. This clearly s/b top on the list. Deeper is better. I think you'll find that dealers are pretty consistent on this, unless instructed to do otherwise.
2) Everything else s/b secondary. But some other factors to consider. Negatives which would lead me to trying to avoid a dealer:
a) Scrapes b4 cards hit the board. If u can't recognize each card, that's bad.
b) Doesn't show burn card and not loose w/ card at back end.
c) Talks too much. Distracting and slows game down.
d) Bad on calculating payouts. Don't want to have to re-check their math.
e) Sloppy deals. Can't hold the cards, slows down the game.