OP, as for stability
stability varies so much between people. It’s body weight and where it’s distributed, and an innate sense of balance that is very individualized.
So folks can give impressions - and there are many good insights here - but not one of us is you.
go out and paddle them 
Paddle them empty. Paddle them w. a few drybags full
of heavy stuff. Paddle into the wind and w. following waves. Lay back, edge them, climb on their backdecks back into the cockpit, etc. Roll 'em. Brace 'em.Do it all. Get wet. Then see how they feel on land when you lift them up to the height of the roof of your vehicle (unless you’re using a trailer).
Notwithstanding what the good SactoBob has posted, I’d get the boat that feels on the tippy side when first paddled, bec. w. butt time in the boat you can paddle the tippiness out. But the boat that is dead on stable from Day One is, for me anyways, the boring barge I never want.
And since I am small, on the extreme end of the scale as to paddler size, all of these boats (Cetus of all flavors, Quest, and Bahiya) are too big for me, so I can’t make any useful comments about them other than to say that P&H is a British builder who has high quality standards and offers beautifully finished and appointed boats.
Thanks
Thanks so much for all the input.