I have used a few and found that the less exspensive ones seem to be not as accurate.
I had a sears model one once that was a decent testor,
But if they are within a few lbs you will be ok. Really you are looking to see the difference between the cylinders more than the number. Now a leak down testor that is one item that I tried to save a penny or two and was not happy spent a good chunk and have a product that is very accurate . One thing that I have found with the compression testors is that the scharder valve can go bad and give you faulty readings. It is a special part you cannot use one from a tire it will thread in but has a much higher relief rate.
i have an "optilux", screw in, brass fittings, handle compression release, good german quality, had it 20 years but it was expensive. shame their dwell/ multi meters were absolute garbage, a piece of oriental rubbish they had rebadged
I got one from Fleet Farm. Only used couple times on sled. So can't say much. Around $25 I was looking for difference in cylinders. I would think if in doubt, check it few times for repeatable #s. Need to do it with same engine temp.