Except when your homo (Cre+ f/f male) has some sort of phenotype that
affects
breeding, using a het (Cre+ f/wt) may be better. The downside of this is
you get fewer experimental mice but you can overcome that by setting up more
breeders. Also this strategy has built-in controls for Cre toxicity and you
don't need a separate Cre wt breeding line ongoing as a control.