For now, checkmytrip displays more information (in many cases, the BA site won't even tell you what seat you've been assigned ... even though checkmytrip does). In the future, BA says that they're going to enhance this facility, but right now it's not very informative.

What does "Status:" say on the checkmytrip page for each of your segments?

I've had flight times change, and the status on checkmytrip changes from "Confirmed" to "Confirming change in time" (or some such wording) ... and the BA site will display an error message if I try to access the booking.

Just one of the many mysteries of ba.com ...