Lengthy essay follows:
Hope my assessment here is accurate, here goes:

Is the padding on the Evolution just on top where the sit-bones rest?
Pretty much. It runs down the entire length along the outside ridges, but doesn't continue on the inside of the ridges. It is quite thin on the nose. If there is any padding continuing around the outside edges of the sides of the saddle, then I can't feel it.

Does the padding on the Stratos go further out to the sides/edges of the saddle?
Yes, it does, it continues on the inner edges of the ridges and also on the outer edges of the sides of the saddle but a bit thinner than on top.

Do you get any give in the padding when you push down on either of these saddles with your finger?
When you push on the Evolution, it doesn't indent very much at all. It's not like there's none, but the Stratos indents quite a bit more. Not as much as say a Terry Butterfly - but there seems to be a noticeably thicker padding on the Stratos. The Stratos indents more on all areas of the saddle ie the back, the ridges, the inside ridges, the outside edges and the nose, all to varying amounts.

Does the shell have any flex in it? If you were to take it in your hands by the sides, does it bend at all it you push down on it?
Both models have some degree of flex, I would say the Evolution slightly more. If you press on the centre of the saddle, the Evolution would flex downwards more so. Not to the extent of the Specialized Jett, it seems to my experience that saddle has more flex than any I've seen. On the Stratos it's not much flex when pushing on the top, but if you grasp the sides and pull outwards, both saddles have some movement.

Hubby was previously riding a fizik saddle, I can't remember which one, it came standard on his Giant TCR Comp when he had that.

does have a sweet spot for sitting. You kind of fall into it because it has a natural, anatomical dip.
This is hard to say, there is naturally comfy position where you kind of settle yourself into the channel - but I've comfortably moved fore and aft dependant on whether I'm in the drops or sitting up.

I've had no experience with the Arione, but it seems to be a popular choice amongst males and it seems to be the one that bicycle fit experts seem to recommend. I don't know about women, it seems to be that most of the women I know go for saddles in the mode of the Selle Italia Lady Gel Flow, quite wide (150mm or thereabouts) with lots of padding and/or gel and weighing in at approx. 300gr. I have a couple of these myself...

Assos....I give it my very highest recommendation.
oh how annoying... I'm now in a dilemma as to what's more important. My desire for the ultimate bike short -v- the ethical stand I took when I emailed Assos that I would not buy any of their gorgeous gear until they stopped using seriously underweight models in their advertising/catalogues. This situation continues unfortunately. While I ponder my thoughts on this, I've found a great price on the the Assos H FI Lady half shorts at www.ribblecycles.co.uk for roughly US$145 (AUS$183) incl. international shipping, which is very competitive with the Louis Garneau etc. on TE, in fact better than when you add on TE's US$35 international freight charge, which is total overkill IMO for one pair of shorts... (Ribbles is US$16.50 for the same service). I can't find any info on what type of chamois is in the Etxe Ondo shorts, so won't take the risk on them at this point.

Hope that's given you a clearer idea of the Strike saddles...