You should Jack of All Trades

You will not be slowing your opponents down much, because they are buying Jack of all Trades as well, and will just trash the curse you give them.

DoubleJack/Big Money crushes attacks.  Sea Hag?  Trash the Curse.  Militia?  Draw back up.  Rabble?  Chuck the Victory card.  And all throughout it’s gaining Silver.  Attacks barely matter at all to DoubleJack: in the simulators,* it obliterates Sea Hag/Big Money and DoubleMilitia, solidly beats ChapelWitch and ChapelMountebank, and goes toe-to-toe with DoubleMountebank and DoubleWitch.

You should play Jack of All Trades

You will not be slowing your opponents down much with Witch, because they are buying Jack of All Trades as well, and will just trash the curse you give them.

DoubleJack/Big Money crushes attacks.  Sea Hag?  Trash the Curse.  Militia?  Draw back up.  Rabble?  Chuck the Victory card.  And all throughout it’s gaining Silver.  Attacks barely matter at all to DoubleJack: in the simulators, it obliterates Sea Hag/Big Money and DoubleMilitia, solidly beats ChapelWitch and ChapelMountebank, and goes toe-to-toe with DoubleMountebank and DoubleWitch.