I know this is the ultimate fence-sitter position, by why can't folks just enjoy both?
I prefer Tate to La Torre, but there's no denying that La Torre can perform the songs in the original key. No, they don't sound as GOOD as how Tate did them in QR's prime. But there are a variety of factors -- Tate back then was untouchable. Everyone knows it. His voice is also very different than Todd's. Todd's voice is thinner. He can hit those notes (not as clean), and hold a few, but his voice is just naturally not as...full...as Tate's was back then. There (is/was) a power and warmth from Tate's early years that Todd has never been able to duplicate. And it's unfair to think anyone can.
Todd has his own unique voice, and is incredibly gifted. I personally wish Queensryche would just focus on the three albums with him, and just pepper the set with a few of the old classics. If they generally do 15 songs, make 10 of them from the three La Torre records, make five of them the "must play" classics of Queen of the Reich, Take Hold of the Flame, Eyes of a Stranger, Empire, Silent Lucidity.
Make the rest of the set the stuff that was recorded and written specifically with and for La Torre. Arguably, to my ears, the performance would be better. That's never going to happen, because the band believes (and probably correctly) that people expect the old material. That puts La Torre under the spotlight continually to replicate Tate's past. And frankly, while he's done an admirable job, that's really an unfair expectation from people.
That said though, many people think La Torre is "just as good" as Tate back in the day. Obviously, that is subjective. But the more people that think that when they see them, the better it is for Queensryche.