Fold quality is the whole purchase

On a fixed reformer, rigidity comes free from the frame geometry. On a folding machine it has to be engineered into a mechanism that also has to open and close hundreds of times. That is a genuinely harder design problem, and it is where cheap folding reformers fail.

Test it the way you will use it: fold and unfold the machine several times, then load the carriage and check for movement at the hinge. A good mechanism locks positively and feels like a fixed frame. A poor one has a small amount of give that you will feel on every repetition.

How much space you actually save

A folded reformer typically occupies about 2 ft × 4 ft of floor rather than 8 ft × 2 ft 3 in plus clearance. That is the difference between a machine that dominates a room and one that lives against a wall.

Be honest about whether you will fold it. Folding takes one to two minutes each way, and the machines that end up permanently unfolded would have been better bought as fixed frames — cheaper, stiffer and quieter.

Weight is the second constraint

A folding machine you cannot lift is not portable. Aluminum folding reformers run roughly 60–85 lb; hardwood folding machines can exceed 110 lb. If one person needs to fold and move it regularly, the weight matters more than the folded dimensions.

Check whether the machine has transport wheels on one end. Being able to tilt and roll it changes the practical experience far more than shaving off a few pounds.