I have been using flats for the past 15 plus years. What started out as an experiment resulted in all of my basses having flats, TI Jazz flats, fitted. I now find it most uncomfortable playing a bass with round wound strings. I guess I am hooked and will just have to live with it. In my opinion the older the strings get the better they seem to sound, my 1977 Precision has a set that are over 10 years old.
I don't play slap but would guess that these are not ideal for that style, if you like a more vintage bass sound, something like 60's Motown, Paul McCartney etc then it is probably worth giving them a go.
i did fit a set of labella tapewound to a Brandoni accoustic bass and I'm rather pleased with them at the moment, but not pleased enough to change fron flats on the various electric basses.