...They have different optics and different shutters, and I haven't been able to compare results on film yet.
My Autocord is every bit as beefy as my Rolleiflex, and as smoothly operating (or silky-working, if you prefer). I've never handled a Rolleicord, but if it is less beefy than a Rolleiflex, then it is also less beefy than an Autocord.
I think you'll find the Rokkor gives the Tessar a good run, if not besting it. My Seikosha MX Autocord is a wonderful camera.
If you want to see why your Autocord weighs more than the Rolleiflex, take a look at a set of photos I made showing the focusing helix of an Autocord-
http://www.flickr.com/photos/18067251@N04/sets/72157626869741228/
Those are some very hefty hunks of brass. Then lens board is also 3mm thick aluminum, machined, while the Rollei is thinner stamped steel.
The Autocord focus system is an great solution to the TLR problem of having two lenses track each other. I would consider it bomb-proof, in that you pretty well would need to crack the body to throw it out of alignment.
A Rolleiflex (or Yashica-Mat) has nothing with this kind of weight, nor this kind of solidity. At the end of that photo series is a shot of a Yashica-Mat focus rail. A Rolleiflex rail is a bit stouter, better finished, but the basic design is the same. The lens board rides on two of those, one on each side of the lens. Not the strongest.
I was talking to someone this afternoon who has looked into Japanese cameras a lot. He said that there's an idea that so many cameras from the '50s especially, were broken into sub-assemblies for design and fabrication development. So you could have something like this beautiful helical system on the Autocord combined with another system to handle lens board rotational forces...
If you look at the first photo in my series, there is a silver 'dish on the upper right. In this dish is a metal bar across the top edge. The lens board is stopped from rotating in a circle by this bar. The Minolta service manual tells you what to do if there is any slop or binding in this area: take a punch and hit it with a hammer.
Seriously- take a hammer to the camera to adjust out slop or tightness. The official service manual. In the same camera with that beautiful focusing helix!!
This is what Rolleiflexes didn't suffer from. The machine work tradition was longer, the base of knowledge to solve such problems was so much richer than in Japan.
It is this 'total package' that many Japanese lacked for a period. And what leads me to say that Roleiflexes are at a higher level overall. There are internal parts that would show this, also. They simply didn't need to cut corners or pull out a hammer. If it was a problem, there was solution near at hand through either old knowledge and skills or a labor force that knew how to tackle such issues. And it shows...
It also shows its limits in, for example, not adopting a brilliant answer like Minolta's to the focus rails, something that would easily be accommodated by the rest of Rollei's design. Old school, stuck in their ways, lots of machines dedicated to certain ways of doing things that would need to be reconfigured.
Does any of this make a difference in the photos we can take with these cameras? Only in the way that a camera can work well with you or me or anyone else. Or against you or me or anyone else. Each camera is capable of meshing with different aspects of why we photograph.