Glass breakers and seatbelt cutters are almost always better as a stand alone unit. I would go for something like a res-q-me on your keys over a knife that has a lot of compromises. The spyderco assist would be the exception. As an EDC knife, thin and comfortable are going to be better than something big, heavy and designed for people wearing gloves. no point in having a seatbelt cutter that makes you turn the knife funny, or that you never practice with. and to be honest that type of cutter only works when its razor sharp, so its far better as a dedicated tool than part of an EDC which might dull a bit with use. A full blade, even a bit dulled, will cut a seatbelt pretty well.
Partial serration is kinda worst of both worlds in my mind. if you want a rope and belt cutter, then by all means, get a fully serrated sheepsfoot design. But for general utility, even though I'm not a tanto fan, if you are, that will work just fine. a sharp blade is a sharp blade. you want something that is going to work well for your 90% of uses, because that is what you are going to do under stress. and might as well work for the actual tasks you need it for.
Personally I started out trying to get one knife to do it all, and ended up with several that didn't do anything well at all. Including a Trident folder. Over time I realized that a lot of what I thought I needed a specific feature for was handled just fine by a sharp knife. Or were better served by something else, like a big pair of shears, or a rescue hook. On the job I tend to carry a couple knives to do different jobs, partly due to where I live. One handed openers are a bit grey where I live, but I work with ropes a lot, so I have a skeletool CX. Really handy, not so good in the hand for more than a couple cuts, so I also have something that I can do some carving or shavings with that doesn't have to be fast access. Outside of work I generally carry a multi-tool or a SAK. so far has been enough.
