Well the thing to conder there is defensive or offensive?
Defensive 3+ armor save for 1 pt more per model, which can make them stick around a lot longer, usually what you want for guarding Slann plus they are still S4
Or S5 for free which will do a good job hacking into most units, so you'll be killing most things you hit, but then again you'll probably lose more do to the lower armor save. However stubborn makes up for the casualties most of the time in CR.
So really it comes down to the role you want these guys to play