I don't really have a preference, but having done my first couple flights in close to 20 years in the past 3 months, I was struck by how much has changed in that time.
PreCheck and Global Entry weren't around when we went to Bermuda in August 2001. It was a trip notable not only for its proximity to 9/11 - by chance, my bag was searched either before we left L.F Wade in St. George's or on arrival back in Newark, but this happened without my knowledge and I only found out about it because customs had repacked it included a note informing me of this fact inside. - and also because a trip to camp the previous week was the start of an ear infection which burst my ear drum on the plane going down.
Fun times.
However, I quite like the idea of passport control on a train happening before you embark on the departing leg of a trip. With those formalities out of the way, just collect your bags at the destination and you're free to go.
I don't know if the FAA or TSA would consider this too burdensome to implement, but it's an idea.