Realistically the knives listed can never be as good of an EDC choice as the XM-18 because the XM-18 is stronger, nicer looking, better steel (often better cutting ability, certainly better wear resistance, and dependent upon the knife, better corrosion resistance)
Not so fast...
The Opinel:
Yes, the XM-18 is stronger.
No, the XM-18 is not better looking (beauty being in the eye of the beholder and all), the Opinel has an Old World charm that the XM-18 can never achieve.
Better steel? No, the carbon steel of the opinel is an excellent performer.
S30V is different, but certainly not better.
Cutting ability? It depends upon what you're cutting. The Opinel will out cut most modern tacticals on most things.
Better wear resistance? Again, no.
Better corrosion resistance? Yes, I concede this without argument.
Buck 110:
No, I'm not convinced that the XM-18 is stronger than a Buck 110, why do you think so?
No, the XM-18 is definitely not better looking. The buck 110 is a classic for a reason, and part of that reason is its beauty.
Better steel? It depends...the 420HC is easier to sharpen and takes impacts better than S30V (and no chipping issues which S30V can be prone to).
But I do concede that the S30V will hold an edge longer.
Cutting ability? I seriously doubt it. The Buck 110 has one of the best blade designs ever and makes an outstanding cutter.
Better wear resistance? Maybe, I'm not sure.
Better corrosion resistance? No, the 420HC has better corrosions resistance that S30V.
Endura 4:
Stronger? Again, I'm not convinced that the XM-18 is stronger than the Endura 4 at all.
Better looking? Yeah, the E4 is kinda ugly...like a Glock 17.
Better steel? No, I like S30V alot, but I don't think it's superior to VG-10 in the least.
Cutting ability? Again, I doubt it. Sal really did a great job re-designing the Endura to create the Endura 4, and it really cuts great.
Better wear resistance? Maybe, I'm not sure which steel holds the edge in wear resistance...the same with corrosion resistance.
Victorinox...let's use a old model like the Soldier:
Stronger? Sure, why not.
Better looking? No, not really.
Better steel? Again, it depends upon what you mean by better.
Cutting ability? Maybe, maybe not.
The Soldier model is a great slicer, but it will dull faster than the S30V.
Wear resistance? Okay, I'll concede this one.
Corrosion resistance? No. I've never seen rust on a Vic SAK.
When you get right down to it, there's very little to even
suggest that the XM-18 performs better than knives costing 1/3 its price.
I'm not trying to pick a fight, but MrPres asked for our opinions and I really think that he would be better served with a less expensive knife,
IF he's looking to get the most performance for his money in a knife.