joel moskowitz
I have actually done back to back tests of infill Norris's to compare performance. They work, sometimes great, sometimes not so great. However NONE of the famous furniture from England before 1800 or the US or France was made with metal planes. Sure there might have been an odd outlier here and there but except for marquetry, metal planes don't show up in the literature. Roubo thought metal planes were great and wondered why more weren't in use.

That all being said the indicator of performance is fit. Wooden planes have one serious flaw - in use they wear out. Infill planes have two serious flaws - weight on the long ones, and cost. I have tried using the longer Norris's for jointing and after 10 minutes I'm just tired. Also the higher center of gravity of wooden planes makes it easier to keep them square.
But it all works! It really does. My limitation is the limit of my skill not the tools. It's true that these days you can buy a plane shaped object that will never work properly. Or a Wooden Norris that is a collectible for a reason (they suck). Remember of course any Norris you have is at least 70 years old and might be worn out.