Educating self on non-Patek perpetual calendars

[FrançoisCzapek]

One of these days I would love to buy a Patek perpetual chronograph. Along the way, however, I find myself looking at non-Patek perpetuals and perpetual chronographs. For example, I passed by IWC and have been wondering if I would love to wear a Top Gun Big Pilot perpetual (46 mm) or the new Portugieser Eternal (44 mm), though these are interesting choices given the size alone. I'm also looking forward to trying the Lange Datograph Perpetual Tourbillon Lumen Honey or whatever you call it this month, another classic perpetual that respectably can be discussed alongside the Patek 5070 and 5370.

Patek grails are well discussed, but how do you educate yourself on non-Patek perpetuals? This ranges from what distinguishes them mechanically to how they hold value and whether you are better off picking them up used. As a practical question, would you buy a used IWC Portugieser Perpetual in platinum at US$30,000 if you could, on the way to buying a Patek perpetual chronograph at US$250,000 and up?

Honestly not sure how to educate yourself and, for example, there seems to be little meaningful discussion of IWC online especially on the actual IWC forum.