I also have both, and I like both, but my choice would be the mini-grip. As dericdesmond says, it's a matter of taste. Here's my take on it: I think the mini-grip blade shape is more useful for the kind of cutting tasks I encounter. I also find it opens a lot quicker and easier and is more convenient to close than the Delica. I love love love the Axis lock, though I am sure the lockback on the Delica is probably just as strong. Also, both knives have excellent lockup. I'm no steel expert, but both seem to be very high quality and hold an edge very well. The balance on both knives is really good--both of them have a midpoint for weight just about where your index finger falls. The clips on both knives are really nicely done and reliable. One thing that might matter to you is that the Delica's clip can be repositioned for tip-down carry, but the mini-Griptilian's cannot. (I don't like tip-down carry myself.)
Ergonomics is a tough one, because that's going to depend on your own hand and how you will normally handle the knife. The useful portion of the Delica's handle is at least a centimeter longer than the mini-Griptilian's. I have pretty small hands so that's not a problem for me--in fact, I prefer it--but if you have big hands, it's something to keep in mind. The Delica's handle feels clunky to me for a couple of reasons. One is that the handle surface is totally flat. The mini-Griptilian's handle is very slightly convex so that it cradles better in my hand. The other thing is that the mini-Griptilian's handle shape works better for me. The finger choils and the thumb ramp on the Delica seem designed for a grip where you've got your fingers wrapped all the way around the handle with your thumb on the spine. This is great if that's what your chore calls for, but if you want to hold it in a kind of classic "let me peel an apple" grip, it doesn't work as well. The peaks and valleys on the "finger" side naturally force my fingers into particular positions along the handle. Overall, I feel the mini-Griptilian's handle gives me better control and more versatility.
I like the mini-Griptilian's handle material fine, though in all truth, there isn't much texturing for a knife with a name of "GRIPtilian." The front third of the handle is mostly untextured, though not slippery. Some people may not like this, but it works fine for me. The Delica's texture is a lot more aggressive. This knife is definitely not going to slip out of your hand even if you need to apply a fair amount of force.