I have tried both UT and Plasma on my Nexus 5 and they are just not ready - badly. While UT 15.04 might be usable, 16.04 is a disaster.

Plasma is even worse. It is slow, like very slow, nothing works smooth taping, swiping takes too long for comfortable usage. I can try to use both of them, make some bug reports but after a day or two I smack Lineageos back on the Nexus as even trying to use them is so frustrating.

The UT team tackles to many phones and none is prime time ready (for 16.04). Plasma has a very old TWRP and I don't get it why they don't update it.

That being said- this is only my experience full of frustration. Yours may be different.