I'm on the some boat! I love 4 strings, but to me certain songs are much more fun to play on a 5 string. Superstition, I wish, Rock with you, I wanna dance with somebody, Bruno mars songs. Some songs are more negotiable than others. To be honest my band members could care less what bass I bring, ultimately it's my choice. Life is short so play whatever makes the gig more fun!
If you are going the 5 string route and don't want to spend a lot check out these basses:
Sire ($600), Bass Mods ($1000), Xotic Vintage ($1500), Sadowsky Metro Express ($2000).