Close vs. Open Position Chords in Brass
When writing chords in Brass it is usually better to stay in close position voicings rather than in open position. As basically all brass instruments have a natural crescendo and raise in intensity towards their top end, writing open chords (as you would for example favour in the strings) for them will usually create an imbalance with the lower notes falling into considerably weaker registers making it hard for them to balance out the chord.
The only notable exception here are trombones that due to their general low notes tend to become muddy when you put them into too close position in their lowest register so you would prefer open voings there. Still in their middle to high registers, they work more effectively in close position chords as well. Again as always, this is to be understood as rule of thumb. There are cases where other decisions might be favourable. This includes for instance cases where in very soft dynamics you might get a hauntingly beautiful sound out of open voicings (as in such dynamics the balance differences mentioned at the beginning can easily be compensated by the players).