With these descriptions what we often see is pretty much the same thing in both, from Teacher and Student alike, which is the vein-popping super tense sweating dynamic tension that seems to have become characteristic of what people think is Goju Ryu Karate.
My Teacher and many of his ilk would have, and still do, call this sort of display Go Go Ryu because it lacks any sort of balance or depth and often does lead to some serious health issues because of said lack of balance.
This sort of practice DOES lead to Gastrointestinal issues, high blood pressure, not to mention pulled muscles, hernias, uptight aggressive behavior, not to mention it also compartmentalizes the body rather than allowing it to align, which promotes bad mechanics in technique.
When it comes to Tensho we should find a totally different approach because this is supposed t be the 'Ju' of Goju Ryu, but what we find instead is the exact same thing that we find in Sanchin, super hard dynamic tension which promotes the exact same issues.
My Teacher, Dascenzo Sensei, once told me that Tensho was like a Nuclear Reactor smashing atoms in the Tanden, but in a very soft and directed way... It is the SOFT path to the HARD aspect while Sanchin would be the HARD path to the SOFT aspect.
There really should be no great tension in EITHER Kata and the breathing, according to the likes Yoshio Kuba Sensei, Kayo Ong, and others, was originally just a TEACHING TOOL and is NOT how either Kata is meant to be performed.
When going through Sanchin the focus should not be on extreme muscle tension and extreme Ibuki Breathing.
The body should be allowed to align of itself in a natural way that promotes good structural integrity, good mechanics of motion which promote, in turn, UNIFIED Shin, Gi, Tai.
Tension is only for a split second as techniques are completed, and this is only in certain parts of the body that are in harmony with each movement.
Tensho is different yet the same, and one can see this in the fact that it is often performed WITHOUT the punches for emphasis on its' flowing and turning.
The Kata itself is similar to Wing Chun's Sil Lum Dao, almost move for move, which should be a clue as to what it represents.
One cannot hone the Principles of Sil Lum Dao with extreme tension, one has to be relaxed at certain points and taut like a bow-string at others, one leading to the next in succession, again, this was never meant to be extreme and the breathing methods that were once taught (and seem to have been lost on most), while an important aspect, are only audible as a teaching aid.
This Kata is absolutely NOT meant to be performed in the same way as Sanchin, just as Sanchin was absolutely not meant to be performed with extreme dynamic tension.
I did 100 reps of Sanchin Kata for the 100 Kata Challenge on the day that has been dedicated to Miyagi Chojun, but I would not have been able to do this if I were performing Sanchin in the way that most perform it.
It was still EXTREMELY challenging, but not in the muscle-bound sort of way, though it did drain me and leave me nearly crawling.
The feeling is different, almost like doing unbendable arm with the whole body, but you direct sinking, rising, rooting, ect., aspects which also seem to be missing from the modern rendition of the Kata in many schools... Including some schools within my own lineage.