Depends on your needs. For garage use only get a full size one. Needing to use it to change tires while away from home get a small unit to keep in the van instead of the bumper, bottle or even the scissor jacks.
I have used a couple from Harbor Freight before and was not impressed with them. Unit wheels wobble, it may start leaking down soon after purchasing when you are trying to lift and just change a tire. Also when trying to lower the vehicle they have had a tendency to just about drop the vehicle instead of easily lowering it.
Craftsmen are good, never had an issue with the two I have used before.
Other sources would be JC Whitney, Norther Tool, might even check with your local auto parts house and see what they have.
For one to keep in the vehicle I am using two from Wal-Mart. Both do a find job when on the road.
When looking for a floor jack no matter which one you get make sure to have jack stands with it. Never ever trust any floor jack by it self to keep the vehicle off of you. They are for lifting, not full supporting of the vehicle.
I bought the Habor Freight alum floor jack that has the lights in it. It is the jack I carry in my van. After I bought it, I tested it and it worked fine. I hope if I ever need to use it that it works then.