It realy depends on your requirements.
Mainly bridge mode is used for multicast support, Multiple DMZs + FWSM, server initiated connections or for seemless migration from previously installed "bridged load balancing environment".
Some of the differences are
In bridge mode you do not need additional config for "Direct server access" / "Server Initiated connections"
Broadcasts are dropped in routed mode whereas they are bridged in bridge mode.
LB functionality is same in both modes.
Syed Iftekhar Ahmed