Hi Ryomaru...
I agree with morestag. Though they are close to the same size, they are two totally different types of knives.
If I had to choose just one between the two for a "last ditch self-defense tool", it would be the Kaala. For EDC, the Waimea.
Now, if you wanted quick deployment, I wouldn't choose the Waimea as the folder...in that size arena, I would go with a Sirus...the assisted opening makes a big difference.
And, for me, in your desired application...I'd pollute this thread by telling ya what I recommend since it's non-Buck.
Your best bet is never to be in such a situation...but sheet happens (see post 19 & 20 in this thread:
http://www.bladeforums.com/forums/showthread.php?p=5663631#post5663631 ).
But you asked about the two Mayo models for last ditch.
Having said all that, for your first Buck knife, or for anyone that has lots of Buck knives, you can't go wrong with either (as morestag also said). They each are "art" in their own right.
If you'd like, I will post a pic of the two side by side for comparison.
.