I play 80% fretless in my current band, but there are a few songs that are so much easier ( and sound so much better) that I always use a fretted on them. Songs with lots of octaves, and or large shifts up and down the neck can be played a lot 'crisper' with frets. I would say add a fretless, and put the money, or time you would spend on the conversion into a new bass.
my $.o2
my $.o2