Think about future plans before deciding. Will you want to go higher later on with longer coil springs? If you do, get the BB so you can always re-use the bb spacers for a little more lift on top of the new kit you get later on. If this is the only lift you will ever put on your jeep (
) , then go with 4wd's because it comes with 4 coil springs and 4 shocks (that's about it, the picture shows the 3" kit and you don't get all the goodies in that).
Neither is gonna flex more than the other, unless the shocks are longer. Both are 2" kits (actually the spacers are 1.75").
from everyone i've heard using 4wd's springs/shocks, none have ever complained. The dudes at the desk in 4wd's store say they sell more 4wd kits than any other.