I saw Jim in Barnum and was blown away. He was amazing in the production and put his "stamp" on the role that I don't think was ever equalled. I have seen the DVD with Michael Crawford a few times and while it's entertaining.. I thought MC just didn't have the charm (and as another poster said "snarkyness) etc. Jim never seemed to "mug" the audience which was something that bothered my about MC's performance.
I recently talked to Tony Orlando (who did the role on Broadway) and he said that the producers in the US didn't want to spend the money to record the production, so that is why Jim Dale's performance wasn't the one preserved. Which is a shame...
"A little nonsense now and then is relished by the wisest men" - Willy Wonka