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
Bridged Mode:
In bridge mode you do not need additional config for "Direct server access" / "Server Initiated connections"
Broadcasts are allowed in Bridged mode.
There is a Source Nat limitaion in briged mode that only applies to non-load-balanced traffic.
Its also useful in scenarios where its not possible to make any layer 3 changes on Real servers (IP add/ Routes)
VIPs and Reals can be in Same/differnt subnet
Routed Mode:
Easy to deploy when there are many subnet with real servers in it.
Broadcasts are dropped in routed mode whereas they are bridged in bridge mode.
In the same lines if you want multicast from your servers you cannot use routed mode.
Routed mode's L3 separation makes debugging and troubleshooting comparitively easy.
VIPs need to be in different subnet
LB functionality is same in both modes.
Syed Iftekhar Ahmed