I say if you plan to collect, the rarer the better. Like find a first gen iPhone that is 4GB. That wasn't in the market very long and the 8GB version was the more popular one.
Cell phones to me is like shoes. You wear them out for a few years and then you put them away in room for newer ones. The beginning is always the best when owning something. Then it gets old or takes a beating, and then you stop caring. Like the beginning of a relationship. Looking back at my phone history, I don't really have most of them anymore. Either lost, stolen, sold, or given away. The older ones I still have is in one of my drawers somewhere. When my iPhone 4 is retired, I will probably put it in a shoebox with my other older phones I still own.
Favorite dumb phone ever (my phone history included)
https://forums.macrumors.com/threads/1002194/