I prefer U.S. Army Air Service lately, but I do branch out. I'm really a history buff and am interested in all things historical (within reason) Most importantly, are there places with lists of all veterans? (officers, pilots, and not just aces)? Obviously, the enlisted pilots in the U.S., for the most part, are not very well documented.
I constantly buy material, and I am always looking for named items. I wish there was a website with an omniscient search engine that could bring up the history of any individual from the past. I would love to have a story behind each item I purchase. Whenever I ask for provenance prior to purchase, I usually get a song and dance. Very rarely, do I actually get something that can even be remotely called provenance. People just make stuff up nowadays!

It's pathetic. For example, I recently bought a pair of bullion wings from a dealer that even named a specific collection they were supposedly from, and they turned out to be fake. The creep wouldn't even give my money back. There are some real winners out there.
On a lighter note, my favorite items have years, names, specific depots, etc. on them. I don't necessarily need to keep them forever. I have come to the conclusion that I buy them just so I can have a hands on experience and display them without having to worry about freaking out some owner. (It's good to be the owner!) After awhile, I sell them to someone else who can appreciate them, usually at cost lately. One cannot exactly go to a museum and handle the goods. I display them for awhile, let my friends and family handle them, and then pass them on to happy buyers. I've never ripped off anybody, if you're wondering. It's a learning experience for myself and all that come into contact with me. (I love sharing the stories.) Most of the people I know would never hear about these things, hold them in their hands, or even hear these stories if I wasn't forcing it on them.

LOL Also, I always let potential buyers handle the goods in whatever non-destructive means they wish prior to purchase.
It's not just WWI aviation either. I've been collecting historical items from all eras since I was a child. It just so happens I've been in love with WWI aviation the last few years. My family and friends always love coming over the house, because they know there will always be some new treat to play with and hear stories about. I just think you can't beat hands on history. I like reading about things and seeing them in museums, but nothing beats holding them in your hands and examining every last crevice of the item. I just love it. I remember working in a certain National Museum, handling all of those priceless artifacts, and having mixed emotions of joy, wonder, etc. Alas, archaeology does not pay very well.
Ideally, I'd love to live history and experience these things as they were used...meet the people, etc. Any time period. I just love it. This is the second best thing. I would love to get filthy working on a Gnome engine prior to takeoff. I would love to be wiping off castor oil from my goggles as I fly through the air in an open cockpit. I can skip the ingestion of the castor oil, however, and avoid the wonderful after-effects so common with Camel pilots.
Yank
P.S. I can skip getting shot down too, unless I can hit restart afterwards! LOL