will you get better merchandise in a dropped chest than from one bought from the Black Lion Trading Co, or are they the same
They are identical.
Even though the Trading Post shares a menu with the gem store the two are entirely seperate. The Trading Post is entirely for player to player trading, so when you buy a chest from there you're getting one which dropped for someone else. It's exactly the same as one which drops for you, it's just another way to get them (and another way for players who don't want them to get rid of them).
Danielle Aurorel - Desolation EU. Mini Collector.
"If someone really cared, well they'd take the time to spare, a moment to try and understand another one's despair"