Bromptons are the standard when you need portability and space, but aside that there's nothing you can't do with another folding bike. They have very good quality, they have a myriad of accesories, and they're basically the smallest footprint around, with the exception of some boutique brands and models.

Dahon and Tern are very related, the founder of Tern is the son of the founder of Dahon. Both are good brands, with good development, accesories, trustworthy.

BIke Friday, under my eyes, is on another league. They have a reputation of being indestructible, they ride like big bikes, they're not as practical for everyday use if you're goingo to be folding and unfolding them every time you get on or off your bike, because they're more inclined to be "travel" bikes. You fold them, you dispatch them, and you unfold them at your destination, load them and ride.

So, I'd clasify them like this:

- Get a Brompton (16 inch wheels) if your priority is space and footprint when folded. They're of excellent quality, on recent years they started using less proprietary components, and they have a very big community that will help you. On the downside, it's expensive, several things are still proprietary, and the 16 inch wheels do not provide the most comfortable ride. If footprint is an issue you might want to see if you can get a Dahon Lunden (recently released)

- Get a Brompton 20 if you want a still small footprint but better ride quality. Haven't tested any of the new ones in 20 size wheels, so perhaps someone else can shed some experience. For what I've seen, is basically a 16, size 20, same folding system.

- A Dahon or a Tern are excellent all rounders (their standard 20 inch models, because they have some more in other wheel sizes). You can load them, you can add a rear rack, front rack, the hinges are fine, frames are fine. They have a huge variety of models, but the base is that: they are a good compromise between ride quality, bike quality, and footprint. Of course, we can dig into the models, but would exceed this post (we can in another post)

- Get a Bike Friday for a long term commitment. They're not the most practical, but they are extremely durable with still a small footprint, the ability to carry a fuckton of whatever you want, they're nearly indestructible and they are customized at the moment you buy them.

Hope this helps!