In my experience of riding a Tern link D8, the Tern is a nicer ride generally but it's fold is lousy, it just becomes an unwieldy, bulky mass of bike bits that flail around without much warning, it won't win you any friends or praise if you're using it to commute on a train.
On the other hand, the Brompton is generally a little bit less of a comfortable ride, the three speed hub gear doesn't allow you to keep spinning at your cadence of choice, but it's fold is unrivalled, it's lighter than a Tern and it fits in the boot of a small car.