Below is the output for a WAN router peering with provider external Ebgp and also have iBGP peering as well.
Based on the output below i am assuming that best path is the internal ibgp peer since it looks like the provider (ebgp 213.121.150.121 AS 3854) is doing AS Prepending ( sending Community: 2856:10 2856:104 5400:3001 5400:3002 5400:3300 to us). So by design bgp will look at lower AS-Path instead and will choose the internal. Without the prepending, then the ebgp will be the prefered of course.
(Site 1)
bgprouter1#sh ip bgp 24.37.192.0
BGP routing table entry for 24.37.192.0/18, version 142343011
Paths: (3 available, best #3, table Default-IP-Routing-Table)
Not advertised to any peer
3854 5400 5769
213.131.18.12 from 213.131.18.12 (195.99.125.167)
Origin IGP, metric 10, localpref 100, valid, external
Community: 2856:10 2856:104 5400:3001 5400:3002 5400:3300
1478 5769 (This via another ibgp nei)
192.168.45.88 (metric 3) from 192.168.45.88 (192.168.45.88)
Origin IGP, metric 4294967294, localpref 100, valid, internal, best
Francisco.