In order of what I prefer:
Vernier: There's nothing to gum up, they maintain their accuracy unless someone screws up the jaws.
Dial: They're what I'm used to, they're fast, reasonably accurate with skill and there's no batteries.
Digital: They're OK in their own way, but I only tolerate the high-end ones that are coolant/water proof and have batteries I can readily find. My biggest beef with many digital calipers is that they present false precision to the operator.
By all means, get a set of gage blocks for reference.