Depends on the kind of bettor you are. Both are great outs but I think Bookmaker is primarily for sharper players who want to avoid getting limited as well make bigger bets on a wide variety of sports. To me JustBet caters to everybody and I think you have more options if you're one looking for good bonuses. They are known for their bonuses but imo they're almost as good as Bookmaker who's been around longer and is widely considered one of the best offshore outs you can have.