I love my Izula, and I'm pretty fond of my Scrapivore too. I wouldn't turn around for the difference myself, but they're both fine little neck knives.
Doesn't the Izula have a shorter blade?
My real complaint with all of the listed knives is the blade length. The handle of the Warden is comfortable enough for the knife's intended purpose but they lack blade length. We've used them for food prep, and they just don't have quite enough blade. Another 1/2" would make them much more usable.
I sold all of my 'Vores because they hurt my hand. I still have FIVE Wardens, but plan on thinning that herd in anticipation of some other small offering. (I just couldn't warm up to the 311 and the 411 is a great knife, but too big for "minimalist carry", etc).
The Rodent Solution was nice, but very "butt heavy". The grip made the blade difficult to use.
I'm going to try out my new Leaner Meaner. This has real promise