I agree with everything 'cept the t5 being unreliable, I have been abusing my t5 for about 50k miles. No track stuff but I'm not afraid to dump the clutch from a roll, I'm also smart enough not to use sticky tires. Just know it's limits.
Obviously, I care. Suit yourself if you don't use a dyno to compare the pros and cons of parts that you might choose between, but I do, and so do many others. What good is the information? Well, for starters, this is my hobby, and I ENJOY obsessing over the details. I enjoy optimizing my combination to get it to the goldilocks standard for me - just right. Transmissions are also a big amount of money to spend. So, I appreciate a full understanding of the pros and cons before making my decision or advising others to make the right decision.Who cares about a dyno number. We only use it to tune. Say the T5 is more efficient but it's slower at the track due to wide gear. What good is this information?
We all modify for different reasons. T56 shifts better, T5 is cheaper, T5 is great for wide power bands, T56 will handle way more power, T5 is unreliable etc.
So even if there was, and probably is a slight loss. The T5 and T56 Magnum close ratio have very different gear ratios. So a back to back comparison is not realistic. Some engines hate the big rpm drop between gears, some don't care.