I have a season pass here because they give a really good discount to college students. Anyway, During the Week, JF is open 9am-4pm and BB is open 3pm-9pm, 10pm on fridays. On the weekend, JF is open 8am-4pm and BB is open 8am-10pm. One pass will cover both, most people go to JF in the morning, then head to BB for night riding. You still have to pay the toll if you want to take the route through the development, but if you have a gps or something, you can easily go around it and it only takes like 10-15min to get from JF to BB.
As for the difference in the two mountains. JF is alot bigger than BB and has more challenging trails, (not that challenging, this is PA) and it only has one park in it. Which if you read my thread called "Respect?" you'll know what your getting into there. During the week though, its pretty empty, def better riding then the weekend so you might be ok. BB is smaller but is pretty much all park, lots of jumps and boxes and rails to hit there with a few trials in between. Hope this helps. If you have any more questions let me know.