2-4 mph has not been my experience. I have taken special note at several showcases. Jugs gun next to a Stalker. 90% of the time they have read the same. On occasion, Stalker read 2 mph higher than Jugs and on occasion, Jugs read 1 mph higher than Stalker. I'm not sure why everyone quotes the 2-4 mph difference with Jugs and Stalker, but my experience has been they are very much the same.
FWIW, I have also seen 2 Stalkers next to each other giving different readings by up to 2 mph. I think you are safe going with readings with either.
Recently, I have seen guys using the new Pocket Radar. You have to push a button to activate it and if you are off, the reading will be off, but once these guys got their timing down, they were giving the same readings as the Stalkers. Not bad for $200.