I personally don't feel it takes away power at -10. I don't trust myself enough so I asked a pro driver on the Ring if he feels that TC limits power. He said that it does something with brakes, but he believes it's just ediff works to stop wheel hops and he didn't feel any TC related power cut.Good point. I've only used PB on a RWD, which I've just traded in for a performance. I've only heard from others that TM still robs some power out of the corner, but haven't tried it on track myself yet. I'm interested to see the difference and will be installing the PB on my P and testing it against TM at Buttonwillow in a couple weeks. Will mainly be a gut-feel test, but I'll have the scan my tesla data to review afterwards.
Without track mode or even at 0 stability control with TM the power cut is undeniable even it releases full power much faster than on ICE. As far as I know MPP doesn't claim there is any advantage in party box vs track mode except ability to run full power cooling while finishing supercharging. And I hope that Tesla would eventually add this option to keep track mode while in charge, because you really lose a time and charge between rides or have to go with everything too hot.