[Freeswitch-users] difference between bridging with 'user/XXXX@YYYY.com' and ${sofia_contact(XXXX@YYYY.com}

what is the difference between bridging to a UA using 'user/XXX@xxx.com' and ${sofia_contact(XXX@xxx.com} ? i noticed things like presence (esp. with SLA) work better with user/XXX@xxx.com I also noticed the pickup dialplan app (,pickup/XXX@xxx.com) doesnt work with the 'user/XXX@xxx.com' it only seems to work with sofia_contact bridge Can anybody test or verify this? Thanks. RJ