I bought the 3m rail, I like it very much. I have shorter rails (one from the MFT and a holey). If your breaking down sheet goods, it's good to have both. I will have both set up, one for rips and one for cross cuts and switch back and forth. If you have to keep breaking one down during this, that will get old basically instantly. I wouldn't want to go doing cross cuts with the 3m rail.
I really don't get the storage concerns very much. It's not like many people have many rooms with no walls longer than 10 feet. I just place it on my lumber racks with 2x4s and PVC pipes. Other spots have have 2 screws in the wall and just hook it in the groove.
My real issue is if you need to take it someplace, being half the length would be nice, and long term storage (if you pack your equipment away for periods of time). That's where it would be nice to have several identical rails around 1m long that connect very well, so when working one can assembly a short and long rail, do the job, then break it all back down for storage.
But as long as your not planning an road tripping with your rail, or have a requirement to be able to put it all away in storage, I don't see an issue with the long rail. Folks just need to remember rooms are generally longer and wider than they are tall, so stop trying to store them vertically.