What to use for undercoating?

http://www.u-pol.com/product-cat/83/raptor™-bed-liner.htm .....lots of guys use this stuff

Or
http://solutions.3m.com/wps/portal/...E3E02LECFTDQCEK3_nid=RM3XV860K8beZ024MJP62Rgl ......my brother's shop uses 3M stuff