If I wanted to know what routes local BGP peer sends to remote BGP peer, I would use "sh ip bgp neighbor a.b.c.d advertised-routes". Unfortunately, this does not really show what exactly is sent: for example if you adjust MED with route map, the "advertised-routes" command does not show it; also it does not show confederation sub-AS numbers converted to real AS when peering with external peer.
Is there way to really know what one is sending out via BGP?