The other side of the coin is your dynotuner is tuning in an environment. We ride in multiple environments. I live at sea level and the humidity is extremely high in the summer. When I ride to the mountains and in drier weather the bike has an opportunity to make adjustments for the altitude.
AT Basic & Pro are two entirely different animals.
Your dyno guy is using pro ~ Wideband Sniffer. In your tailpipe ~ Can he tune the cylinders individually? I feel that I can do a more accurate job with AT Pro since I am tuning cylinders individually.
I am also accounting for temperature, humidity, fuel, and altitude.
Also, if I decide to play with timing (which I do). AT Pro will adjust the AFR's for that.
AT Basic with a great running bike is probably left best untouched.
I can tell you from experience with my bikes and miles ridden, and friends, there are many miles with great runners that have never been on a dyno.
Heatwave's 117 PCV & AT
My S&S 124 ~ PV and AT Pro
A friends 103 with woods 555's, FM's headpipe, and breather.
I'm sure a professional dyno guy would be able to squeak another HP or two out, or even another few pounds of tq.
So there lies the question, if I'm agreeing a pro dyno guy can make it a bit stronger why am I so stuck on AT.
I prefer not to use the dyno's, my bike runs great ~ If I can't outrun you where I am at I'm thinking the dyno guy with a bit more probably won't get me there either...
What about the altitude, ambient temps, fuel variance, and relative humidity.
These are factors none of us can control.
Basic won't do these as well as pro.
I am running a PV and will run pro, I will probably tinker with timing a bit, and a few other things. But at the end of the day I'm happy with the bike, the fact that the bike has not had to spend a day on the dyno, gambling that this dyno guy really understands his profession (I know there are great dyno pros ~ but there are some quacks also).
I don't really care about numbers, to me it is about 50k a year of rideabliity.
But don't try to pass me unless you think you can outrun the 124 for a few hundred miles