Will you have telephone support 8 am - 5 pm Monday - Friday? During your warranty period, this service is free.
Compare the weights of the machines you are considering purchasing. Lighter weight machines generally are made with a weaker frame and weaker parts which lead to failure.
LENGTH OF WARRANTY:
One year warranty is a standard. Is your supplier confident enough in his product to offer an extended warranty?
FOOT PEDAL VALVES AND INNER VALVING:
Ask about the materials used to make the valves inside the tire changer. Metal valves last longer with much leaking and overall trouble.
Where there is compressed air, there is moisture. An inline oiler is necessary for many years of service.
A clip-on air hose leading up to a filler box and gauge on the machine prevents your hands from being near the tire during inflation. Less expensive inflators have a filler gun and gauge (one piece) that require hands on top of the tire at inflation.
Consider max and min wheel diameter, max wheel thickness, overall tire and wheel diameter, bead breaker, etc.
YEARS IN BUSINESS:
Go with a business who is consistent with the same business and has a history of customer service and has proven it over time.
Does the company stock parts, can they ship them without delay, can you reach them with a phone call.
SERVICE AFTER THE SALE:
Can you depend on service and help after the sale? Make sure you buy from someone who has a store and warehouse with inventory to support your needs after your purchase.
You may need to learn how to set up and use the tire changer. When you buy, make sure training is offered for your new machine.