WHen I was in the market for a mini.....narrowed in on the 331 sized machine.
Saw a few x331's and they all seemed to be older machines. Like they were just a previous version of the 331.
In the vintage I settled on (15 year old machine).....there were 3. There was the standard short arm 331, the long arm 334 (which I have) and the 331E which had the extendable boom. I also have one track motor that slightly out paces the other. Say if I started at the the corner of an endzone on a football field and tried to drive straight down the sideline.....I'd end up about at the fieldgoal post without making corrections along the way. For a 15 year old 3000hr machine it isnt worth the time/money to correct the very minor annoyance