For me, it's gotta fit as I ride them all, some only on special occasions, but they all see time on the road or dirt. Also important is aesthetics, it must have beautiful lugs with a big bonus for other features such as twin plate fork crown ect...
When I initially started collecting I had the italian bug which morphed into the Italian track bike bug, however I soon realized that riding track bikes on the street for long distances just wasn't as fun. Most were sold off to fund my current obsessions. Today, the collection is a mix of Rando, go fast, mountain, gravel do all with a strong affinity for the small american, Japanese, or french builders. Trying my best to keep under 10 and failing.