Both Rift and SWTOR are free to play. Their plans are wildly different though, specifically what subscribers get. They can be broken down into two different philosophies, one where subscribers get everything they had before, the other where subscriber get that and bonuses.
Rift's subscriber program is called Patrons.
Every Patron receives a store discount, extra Loyalty rewards, and priority queue status, plus special bonuses to currency, mount speed, and various types of experience. In addition, Patrons have improved daily log-in rewards and exclusive weekly log-in chests that provide the best chance at bonus currency and premium items. Subscribe today for access to all of the following benefits!That's a pretty good summary, by subscribing you get all sorts of bonuses. Trion went with the honey route.
In SWTOR, subscribing basically gives you access to everything plus an allotment of Cartel Coins. By not subscribing, players get the stick, as in they face restrictions. So the major reason to subscribe is not to be restricted.
Which method works better? It's hard to tell. I have no idea how many patrons and Subs Rift has, nor how many f2p conversions each has. I prefer Rift's method, as the bones are very nice and it makes me feel like I am getting something for my sub. That being said, I am subscribed to SWTOR and not Rift. Go figure.