Could go either way. Rhythm or lead? I can name far more guys who use a JB than a Custom, though.hard rock
JB (Jerry Cantrell?)grunge
Could go either way. Rhythm or lead?metal
JB (Alex Skolnick?)thrash
What's the difference between metal and heavy metal?heavy metal
I have no clue.alternative
Depends on the guitar, the band, the style of music, whether there's another guitar player and what pickup is being used by the other guitar player, in addition your role as a player. The amp and cab also make a huge difference. Some players will naturally gravitate to one over the other. I've used both. If my job is to blend in without drawing attention then it's the Custom. If my job is to stand out then it's the JB.Even the JB isn't bad for rythm.
My vote goes to the Custom for the bridge position. As you can read above, both the Custom and JB would work for the styles you are after, it's a matter of personal taste.
Check some sound samples of both the Custom and JB and see what appeals to you most.
Really just depends on if you want JB punch in the middle, or Custom scream and thump on the highs and bottom.
If you are in a 1 guitar band, I like the Custom's EQ better. The JB is good for a 2 guitar band.