Layer 2 vs. Layer 3 roaming

[xxgla]

We have a large network with AP350, and those do not support Layer 3 roaming.

I would like to know what is different in latency and functionality between Layer 2 and 3?

There is mentioned a WLSE in the Layer 3 design, but is it needed?

We are about to by WLSM and Sup720

Is there some technical document whish you could recommend?

Best regards,

Glenn

[#2]

Some related documents.

http://www.cisco.com/en/US/netsol/ns340/ns394/ns348/ns337/netqa0900aecd800fad5c.html

http://www.cisco.com/en/US/products/hw/wireless/ps458/prod_technical_reference09186a00801c5223.html