The phrase "dynos vary" means alot.
My old stocker 12R (Akra, PC3R, K&Ns). Made 171/96 with the stock pipe, no PC. When it was mapped with the Akra and PC, it made 170/95 on the SAME dyno. However, it picked up a consistent 3mph at the track, that's real world horsepower. On another machine it made 161rw. On another, it made 164rw. ALL DJ250s. Then, on ANOTHER machine it made 174/93. Dynos VARY... sometimes greatly.
A friend of mine has one of the magic 184rwhp piped/PCd 12Rs. On the same machine my old 12 made 161rw... his made 160rw. No changes, just different machines.
Cause there is no way my buddies 1290 motor is actually up almost 15 ponies compared to my 1270 motor bike.
1287s typically run stronger than 1270s. Depends on what all is done to the motor, and who built it. More specifically, head work and cams. 15hp difference is possible, but only if one has the head/cam set up, and the other doesn't.