Well based off of my notes, the GT-Q turbine is a 79/68.5 mm turbine wheel as opposed to an 82/75.2 mm turbine wheel for the GT-42R.
The GT-S turbine is an 81.3/75.2 mm wheel
The 71GTQ is usually used with a .81 housing, as opposed to the 1.01 or 1.15 of the GT42R (via garrett). Based off of these numbers, the only way that I could see the GT42R having a prayer of keeping up is the fact that you're talking about the ball bearing version.
I don't know how much of a difference the ball bearing is going to make, but every car I've been in, or owner (of the 71) I've spoken to, loves the turbo and they come online incredibly quickly...and are super linear.
looks like Cang Ly is using 1.06 AR. I wonder if 1.01 AR helps much. From looking at his dyno sheet, that GT42 does not spool until 5k rpm. I was thinking that it would spool a little better since it is a newer design compressor and exhaust wheels.