There is no 100% perfect answer to this, because it is possible that new things might be added to the 2nd Edition Campaign that could make it so that one might wish they had waited, BUT...
I would DEFINITELY (if it were me) put all my backing into The Heat because I would want to get The Kit sooner (MUCH sooner).
Just for fun, I would ALSO watch the 2nd Edition campaign carefully to see if something interesting popped-up that I really wanted.
Maybe the "Naked Guy in Traffic" card will be added to the mix during the 60-day campaign at some point, and maybe that is something YOU (any given backer) would want to not miss out on.
In which case, you could back the 2nd Edition campaign just to get that one card (cost might be $4 let's say). That one card would then be sent to you when the 2nd edition is finally ready and all the rewards are being sent out.
The Heat rewards will begin shipping out to backers in January 2014 (at the latest).
The 2nd Edition rewards might not go out till much later in 2014.
So delivery times could be the better part of a year apart.