When would you use a splittail swimbait over a pattle tail swimbait.

For me it’s water clarity. The split tail doesn’t vibrate the water nearly as much. I get more bites on paddle tails by far in local dirty water.  Swimming TRig or on jig. Even hopping some on retrieve. 
 

The split tail does much more for me in ponds or tanks that are clearer. Swimming slowly at different depths, but I can actually see it. 

I always throw a boot tail from 3.75" to 7"  catches lots of fish and big ones.

As a trailer, I opt for a paddle tail in the spring and again in the fall. Summertime, it's a split tail, or no trailer.

I've never used a split tail as anything but a trailer. Fluke style baits is a whole different animal.

I use split tails when I want to fish faster

I use both in clear....if water is dirty I will gravitate toward the paddle tail for the added vibration.