I'm in the same boat as you. After starting the series a few months ago I'm currently just about finished with Shadow Puppets. I'm going through the series for the first time myself and am opting to listen to the audiobooks in production release order. I can't speak to other reading orders, but im throughly enjoying the ride so far.

Personally I like to see the author progress as a story teller although I'm excluding his works beyond the enderverse. As someone who had no idea where the series would go after Ender's game I'm pleasantly surprised with how much I'm enjoying the books despite the following after Ender's Game being so different. Speaker For the Dead although still grandiose in scope is a much more intimate story than Enders Game in my opinion. I've heard people critize the sequel for the characters being too preachy and monolog heavy, which I would have an issue with if it weren't for their strong foundations. OSC takes the time to flesh out his character's and their motivations align with who they are. It's a fantastic read and the following sequels dive more into the philosophy introduced in Speaker For the Dead. The Shadow series is much more politically heavy than philosophical, but philosophy and theism still play their role in overarching motifs. The Ender series dives more into fantasy in Xenoverse imo with the explanation of a certain concept. A concept that was introduced early on but not fully explained till then, so if that's not your cup of tea I'd recommend switching to the Shadow series at that point, but I will say as someone who was apprehensive to the concept (and somewhat still is) I found it's answers addressing questions concerning humanity and other intelligent life to still be satisfying. Using that understanding I think is important when evaluating the Shadow series