Does the Stealth Tec have baffles in it? Those keep it from doing so much of a beach ball effect?
Hard to describe. It's not baffled. It's shaped better.... the way it wraps the torso and is secured at the harness and top 'plate' of the wing. It's a neater solution. Subtle things.
The Apeks WSX doesn't really innovate much beyond the concepts first seen with the Razor. Beach ball wasn't tackled. It wasn't a big issue with the 25.... but, in my opinion, it should have been properly addressed with the 45.
A friend, and sidemount instructor, dives WSX-45 here... he felt compelled to send the rig away to a sewing shop and got some custom modifications on the wing... and also some custom harness hardware made.
I think he's happy with it now... it certainly improved the beach ball. He's a big guy...and still felt the WSX-45 wing was oversize (dimensions, not volume).
Not yet seen/tried putting someone very petite into one... I'm honestly scratching my head how that'd work out ...?
The Stealth Tec, on the other hand, is much more discrete when filled toward capacity. It's a step beyond, IMHO.
Some small refinements here and there.... which point to some genuine user expertise driving the design process. Like, for instance, the small tabs in the upper wing that you run your bungees through... and go a long way to keeping your upper wing flush to the back. Small design touches... that totally hit the nail on the head...
However... worth noting... that 'beach ball' is primarily an aesthetic issue. It's not something you'd particularly feel in the water. It might annoy you in photos though.
People doing big restrictions in caves and wrecks would be the minority who'd care about beach ball wings from an equipment wear-tear/failure perspective.