if u watch him set everything up and know whats going on, then yeah dyno is good, but the dyno can be manipulated by such people, i would rather ride it and feel the performance than put it on a dyno and see the "possible" performance it makes.
The dyno directly measures the performance you are putting down.........no ifs, ands, or buts about it. Outside of varying loads from terrain, it's putting down the same power on the dyno as it is when it's off the dyno. Judging something by how it "feels" might make yourself feel good, but when the reality comes around that it's actually slower, that's another story. People's PERCEIVED notion of power increases is totally different from the reality of what they are actually getting. Great example being the good old "lightened flywheel gave me power" analogy......or putting somebody on a Shee with T5s compared to PCs. T5s might seem faster with their light switch powerband, but the reality of the matter is they aren't.