RE: Opening post.
I have used limited amount of larger than standard digital caliper, however I have used somewhat larger traditional calipers and two things comes to my mind:
1) There seems to be two types, other one has long enough jaws to measure round objects outside. Great, if you need to do that, but jaws get rather long after 500 mm models, requiring stronger/stiffer/heavier structure AND less play = more expensive. I prefer shorter jaw model, that has square jaws.
2) Play is larger factor on with verniers generally.... I have found that pressing the jaws together near the measurement point with "calibrated" finger force produces more constat mesures, and this seems to me more important more there is play.
Not sure how aplicable this is to 300 model as I don't own one and the stuff at the work is much bigger.
Pekka