How is the 210gr Sierra hollow point's performance on deer sized game? I was recently givin a large quantity of them but know little of their performance.

I've found it to be very accurate and a reliable performer in my Ruger and FA revolvers on game from javelina size through deer, hogs and goats @ 1200-1450 fps MV.

Good bullet for Whitetail, and Tennessee hogs..!!

That Sierra bullet was my first hunting bullet in my first hunting handgun to kill my first handgun deer. Enough firsts for you. At that time I was loading 19.5g/2400 with that bullet to shoot in my S/W 657. I no longer use that bullet but I still load that very load for sons #1&2 and Granddaughter #1. That bullet has killed a double truck load of deer, sheep, goats, and piggies.
BTY here is that first deer:



granddaughter #1 holding a 657 PC Classic Hunter (not the one used to kill this deer, son #2 owns that gun now).

I have been using the Hornady 210gr XTP. Does it give similar performance?

You asked about the Sierra #8520 and I told you my experience with that bullet. I have at least one unopened box of the 210g XTP in my shop (probably two box as that is how I buy them) but I have never loaded one. I use a cast lead 250g for my .41RemMag and all the other handgun hunters in my family don't feel the need to switch from the Sierra #8520. Sorry.