I briefly had both. I've owned a Ranger for a some years and bought a Stiletto for a trip. Both seem to have the same durability and as you've noticed the Stiletto is single tank only with a smaller bladder.
I was able to stuff the Stiletto into an airline legal roller carry-on bag but there wouldn't be much else in there with it. Unless you have one of those Dive Caddy's, I doubt you could get a full set of gear in carry-on. I also personally believe that any airline that checks a Dive Caddy would find it to be oversize and require gate checking but no one seems to address that - I've asked.
So is there a big advantage to diving a Stiletto? IDK. I never did because mine was missing a side bungie and a couple other pieces so I returned it for a refund. Never bothered to buy another one. My plan now is to buy a travel BC for that aspect of my diving and leave the Ranger home.
Other options in the Zeagle line you might consider are the Wicked Lite, the Express Tech soft backplate (will take doubles) or the Covert. The problem with the Covert is that it's WYSISYG - it doesn't use the PFS fit system. Or have storage pockets, the two you see are weight pockets.
The Express Tech will take a bigger wing also if the standard 24# isn't enough. And you can add on either weight system. But it gets expensive fully equipped - to the point where other Zeagle models are as expensive yet have pockets. Which it also doesn't.
If you don't need pockets, the Wicked Lite might be an option also. They're selling out at $300.. I believe the Covert is sort of the Wicked Lite replacement - I don't think the Tribal Markings on the Wicked sold as well as they'd like.
One last option is the Brigade. It's Scubatoys own creation, a Ranger Jacket with an Escape wing for travel. They're also in the $400 range.
Both Wicked's seem to be discontinued also - LeisurePro has them but most other retailers don't. They're no longer listed on Zeagle.com either - I suspect that Zeagle is reducing their offerings after being bought out by Huish Outdoors.
Even if your dealer can't get one, they can fix yours. About all that ever goes wrong with Zeagle's is the inflator occasionally sticks. Buy the BX inflator, it makes cleaning the bladder a breeze - you hook it to a garden hose to flush it. I think they're standard now.