Philosophically - a win is better than a tie, a tie is better than a loss.
Less philosophically - it's your game, play it however you feel like. The rulebook doesn't call it a tie, it says that "both players rejoice in their shared victory", so you can interpret it that way if you like.
More practically - make an estimate based on how well you think you're doing. In MOST cases I would guess that it's better to take the tie - after all, afterwards, your opponent has the first chance to take the lead and you're playing catchup. They've got a one-turn advantage and are likely to win. (If you had the chance to end the game with a tie, with an equal hand they have the option to end the game with a win).
There may be exceptions (say, your engine just got going and they have a BM deck and can't end the game on piles like you can, or you just had a KC->attack turn and saboteured/swindled/otherwise crippled their engine cards, or you've been counting cards and know they have a bad hand, or something) but in general I *think* the tie is the most beneficial option. (Better players, please correct me if I'm wrong!)