Just like pretty much every other question between X card and Y card, it really depends on the deck.
Judge is good for decks that can function without a hand (stage 2s primarily).
Looker's is good for decks that want to just check the hand, or who want to preserve their own hand. Judge is more potent, however, which is why it is generally run in Sableye rather than Looker's.
Lookers is really good for decks that have hand disruption or something specific like that.
Judge is good for hand refresh and just messing with your opponent. Judging an SP deck that just started the cyrus chain is brutal!
Not listed but still an option is PONT. You don't get to look at or mess with their hand, but you get an extra card or two. That can be worth more then knowing what your opponent has in some situations. Especially if you run a deck that simply doesn't care what they have and you're just looking to pound them a little more.