Jumping ship should generally be the rational choice if you have the option.

It's been said before, but if a firm prorates, that suggests they are not in the best financial position and therefore more likely to slash associate pay, delay start dates and even retract offers (yes this happens).

My firm (Fenwick) retracted offers to a huge % of its incoming first-year class during the recession. The fact they're prorating now is raising alarms that wouldn't be raised at Davis Polk or Covington's norcal offices.

The desire to go to a more financially stable firm is a legitimate reason to switch. You can honestly say during an interview that you want to work at a more "high-dealflow" firm after the chaos of the summer.