I have been flying a Tenax4 for the past 2 years, and flew a Rotor Vulto for a decade before that.
I think the quality of construction is pretty comparable for both. I fly lots of high altitude XC, and find sufficient room for everything I need (bags, water, oxygen, regulator, radio, GPS tracker, misc gear, etc). The organization is a little different for each, but it all works.
Tenax4 has the wide backplate. I think it is more comfortable, and might make parachute deployment smoother (less binding, maybe). And, the extra width fills in behind your elbows, anyway. The Tenax4 has a shorter boot than the Havana, which might make positioning on aerotow cart easier. I got the butt-lever dangle-angle option with steel bar slider which is nearly identical to my Vulto.
On the downside, the wide backplate is annoying when buckling the chest buckle, and when squeezing between the rear wires when ground handling. Not critical, just annoying.
The Havana has that sleek machined main-strap roller-bearing slider hardware that Dustin brought over from the Covert. Way cool, and too bad it's not exposed where you can see it. It should be seen, like the engine in a Ferrari
The Havana also has a replaceable boot cone cover (I made one for my Tenax4).
The narrower backplate might seem sleeker, but when I had parachute installed, my Vulto had a bulge behind my arms also (well, on one side anyway).
My Tenax fits better, but that's not a fair comparison (ie. wear, age, better measurements, etc). Make sure you send good measurements for construction.
Anyway, I think they are both good choices. I like my Tenax4 quite a lot. But, the Rotor is certainly nice, too.