C.J.
personally, i would do the 8 hour days, 5 days a week. you'll still be away from your son the same amount of time, but each night you would have more time to spend with him since you won't be off so late. plus, getting home earlier, you have time for dinner, play time, bath time and all the other tasks. as your son gets older and developes a routine, it will be a struggle to spend enough time with him before bed. yeah, it would be nice to have a thursday off, but every other night, you'll have less time with him.
what is good about having the one day off per week, though, is that you'll rarely if ever have to schedule time off work for appointments, but that's the only benefit i see.
good luck. i hope this helps. i suppose it's more of a personal preference, but maybe i gave you some things to think about - neither makes you a better or worse mom, you'll just have to decide what you think works best for you and your baby and family.