Well, all things being equal, the MANUAL R has 10 hp more and about 20-30 Nm more torque. But, off the line in 1st gear they are regulated to 260 Nm in an attempt to maintain traction. Still, a perfect manual R should accelerate harder off the line by about 1/2 sec. Whether or not one would notice it seat of pants is moot though... And most people with some mechanical sympathy can reproduce factory auto figures more readily than sidestepping the clutch on a manual...

Whether either car still makes factory hp could be questioned, so a quick power run on a dyno could tell you quite a bit (find a reputable operator with big cooling fans or you'll risk some unpleasant explaining to do back at the dealers.)

also, it is quite possible the T5-R is not stock. I drove one a while back that had that characteristic "psst" from an external blow off valve - dead giveaway. Or they may have simply done the wastegate actuator mod so you don't make any more max boost but get there quicker by not initiating bleed off so soon. Makes the car feel quicker for sure.

Also, Fueltronics, Chip Torque, Powerchip et al all reprogram Turbo Volvos - so see if you can get the car by yourselves somewhere where you can check inside the ECU without upsetting the owner/dealer.