You might want to try playing some of your songs at rehearals using capos to hear how it sounds in a higher key. You might find that it makes a difference, and you might find that transposing your songs to a higher or lower key only makes them higher or lower, but not really different.
As long as the intervals sound good, and the melody sounds good, and the singers can hit the high and low notes, transposing into different keys shouldn't make that much different.
On the other hand, alternate chord voicings can make a big difference, even though you stay in the same key.