Well, the original question was whether the this particular student trumpet would hold this particular student back vis-a-vis the progress he would make on his Bach. Since none of us can answer that question definitively, we need to generalize for an answer to have any meaning. So, my attempt to make a general answer, by synthesizing the relevant points that everyone else has added here, is that in this case, if the OP continues to practice and play on his Bach, his progress will come there. Whether or not he progresses on the Blessing is sort of secondary. Unless it is just beaten up ("solder all over it") and totally out of tune, it is not likely to hurt his development so playing it while marching should have no negative effects. Other than that, the issues of design, construction, and playability of a student horn vs a "pro" horn (not counting TSO's) have been, and continue to be, debated in other threads on this forum and it doesn't seem that anybody's opinion on that has been swayed even after all of the words that have been written about it... And, I still challenge anyone on this forum to tell me whether my 50 year-old Selmer Invicta is a student, intermediate, or pro horn, either by looking at it, playing it, or listening to it be played by a professional player.