In reply to phja:
So the ethic at J-Tree is prominently trad. There are many bolted lines but you should be aware that the bolt ethic there is to place bolts on lead - not rappel. Therefore the lines can tend to be very run out and exciting. That said all the bolts and lower offs are of top quality. You should also be aware that they have routes that are a mixture of trad and bolts - the bolts protected blank sections. As J-Tree has historic significance in SoCal climbing there has been been a conscious decision not to up rate grades in the park - therefore many 5.7 are in fact 5.9's and so on.
Bishop bouldering tends to be high ball - you will see many of the pad people operating in packs so that they can stack their pads to protect the problems. Have no doubt both venues are world class but would def suggest you take a trad rack to get the best out of J-Tree as most of the super classic lines are cracks and protect great without a bolt in sight.