I usually keep my mouth shut on these types of things if I haven't handled all the knives involved. Since I haven't handled the Ayoob or the Chinook, you shouldn't give my words a ton of weight, but, here are my thoughts as they stand now:
I'll disagree on the one knife I've handled (but don't own), the Gunting. As a purpose-built defensive knife, I definitely admire its design. As a utility knife, I feel it would work fine as well, given Spyderco's usual good job on grinds & heat treat, and the fact that the blade is reasonably shaped. However, for me, one of the most important features of a utility folder is its carryability. Maybe I have to experiment more, but what with the "gunting" projection sticking out, it is not the most comfortable carry folder in the world. I knife that I can't carry comfortable all the times doesn't do it for me, for utility purposes.
I haven't even handled the Ayoob, so I'll caution you to not give my words too much weight here. But I've handled other knives with this basic shape, and while it works out well for some types of utility jobs, it works out atrociously for others. I'm not even remotely sold on this shape for defensive purposes, and for utility, would definitely avoid it. Again, though, I have not handled the Ayoob specifically. Maybe Mas has performed some magic that makes it work great in all contexts. Look at his previous knife efforts and see what you think.
Spyderco has other knives that I'd look at way before these two, if my primary use is utility, with defensive use as a backup. Of the other two you mentioned: The Lum tanto you mention is a cool knife, although I personally have little use for the tanto blade shape for utility work, I would take it before the gunting or Ayoob for utility work. The Chinook, if you can deal with its size and weight, has a very reasonable blade shape and handle for utility work. This would be my top choice of the ones you listed if I were willing to go with something pretty big.
Joe
