There are two basic kinds of single station gym equipment, plate loaded and selectorized. Their functions are similar, but they do have fundamental design differences, each with good points and bad points, which we will try to cover here.

Selectorized strength units are those that have one or more stacks of flat, usually rectangular, weight plates that are permanently mounted on the frame. To choose the amount of weight that will be lifted, all the user has to do is to insert a weight selection key into the weight stack at the point of choice. When the weight is lifted, all of the weight plates from the point where the weight selection key has been inserted and all of the weight plates above that point will be lifted and kept safely in place because they ride on two vertical steel guide rods that pass through holes in the weight plates. If the user wants to lift more weight, he just has to extract the weight selection key and re-insert it at a point further down on the weight stack. On many models, for example, some leg extension machines or some leg curl machines, this can be done without even getting off the seat. The major drawback of selectorized weight equipment is that the maximum weight that can be lifted is limited by the size of the weight stack, which on most machines, can't be upgraded to a heavier stack.

Plate loaded equipment requires conventional round weight plates, normally used on barbells to be hung on the machine in the combination that will equal the amount of weight to be lifted. In order to change the weight to be lifted on a plate loaded strength machine, the user has to get off the unit and physically add or remove weight plates as desired. This can interrupt one's routine and add unnecessary time to the length of the workout. Plate loaded strength machines are usually less expensive than selectorized gym equipment, because you do not have to pay for the weight stack for each machine. Unlike the selectorized strength units, the weights can be moved from piece to piece. Few people outgrow the capacity of plate loaded gym equipment because in most cases, larger and larger weight plates can be used. Additionally, unlike selectorized equipment, even very small plates, like 1 ¼ pound weight plates can be used to fine tune a workout.

In a commercial setting, like a high school weight room, plate loaded equipment is more likely to lead to pinched fingers as the plates are hung, weight plates getting dropped on toes and a floor full of loose weight plates just waiting for someone to trip over them. Also, because plate loaded units take longer to load, they are occupied by each user for a longer time interval than selectorized strength equipment, which means that it will be necessary to have more units to serve a given number of people, which nullifies the savings that might have been made by not buying equipment that has weight stacks, pulleys, cables and weight selector pins. In a home gym, this is not a factor because there will only be one or two users at a time.

All in all, the selectorized weight machines are a better choice for most applications and worth the extra expense.