So, I think you should go hold both. Because I have large glove size hands and the para 3 handle doesn't work for me, the delica does. The para 3 when you hold it the rear bump out of the handle hits right under my pinky and would be annoying.
I think the delica definitely cuts better. It has thinner blade than the thick blade on the para 3.
I think the para 3 is annoying with its choil and handle. Always making you choose between too far backwards or too far forwards. The delica has one handle position and it's always right. The delica disappears in your pocket better. Nice thin design. The only thing the para might be better at with its thicker handle is a bit more to hammer grip. But I carried my delica as a work knife for 6 months and used it in serious work and it was always enough. With the benefits of a better cutting blade.
The k390 is a seriously good steel, can't go wrong there. But if you can get a 15v para 3, it's a mute point.
I prefer the lockback over the compression lock. It's quick and easy to use and unlock abd fold back one handed and is ambidextrous. I do like the compression lock on my paramilitary2, but not quite as much as the back lock.
To me the para 3 looks "nicer" but the delica is going to outperform it in cutting things. I carry an endela everyday now in case you were wondering. Same good design as the delica, a little bigger, still thinner blade than the para 3. Sometimes I take the delica for a spin. The PM2 is in the middle of a fight with a belt grinder loosing its choil.