No, it shouldn't outweigh all other considerations. If you know Bob Wills music, you know why he made a point of changing keys--most everything had the same swing beat and tempo, because it was for dancing, and the chord changes were simple, so he used the key changes to keep interest. (and if you don't know it, you should leave, and don't come back until you do)-

Making a key change within a tune is a very good way of creating interest, but changing keys from one song to another won't do much for you, particularly if your voice is better in one key than the other--so it's more an advisory thing, to avoid monotony.

The most important consideration is to keep it interesting and fun for your audience.