As one or two have already mentioned, it wold depend a lot on the target audience, and how the concert was promoted. Themed programmes can be very successful at drawing in an audience, and can give some unity to the concert as a whole, but even then I think it is important to include some original brass music where possible.
As has been said previously, audiences will often accept, and enjoy, even music that is thought of as "difficult" if it is introduced and explained beforehand. I also like to hear bands playing muic that stretches them to some extent, as that always seems to get the adrenalin going.
By and large, I think it shold be a mixed programme, unless it is a more prestigious event where the programme itself is published in advance, when I would prefer to see more substantial works played. I would certainly be very disappointed if I went to hear one of the "top" bands and heard nothing but lollipops, however well they were played,