Scott, why don't I explain the disadvantages with a dial caliper (as I see them)?
Simply because I can't give a short precise answer and I'd also like to compare advantages and disadvantages between all three types - dial, vernier and digital.
Remember too that, living in Europe, I'm used to working metric so I don't know if dial calipers in inches can be as confusing as the ones that use metric are when they show 2 mm per revolution.
The biggest disavantage of a dial caliper is that it is extremely sensitive to "particles" getting lodged in the rack and pinion. I'd never use one unless I was in a squeeky clean environment

and, when this happens, the caliper is usually useless afterwards. Then again I just don't like them as compared to the easy use of a reliable digital caliper.
I suppose the biggest problem with a digital caliper (and it's accuracy) has been user influence on measurement pressure. It's always surprised me that no (as far as I know) standard or calibration inspection, states the correct or recommended measurement pressure when measuring with a digital calier. As per DIN 862, max. allowed digital caliper length measurement
inaccuracy is 0.02 mm (I'm hoping you can convert this to inches as that is what you are probably used to working with), 0.03 mm up to 600 mm and 0.04 mm up to 1000 mm. The problem with measurement pressure is now solved, although not many know this.
I was at an exhibition in Stuttgart (Germany) a few months ago and saw the new generation of very accurate, affordable digital caliper that have a display of 0.001 mm (0.00004") and an accuracy comparable to a normal (non-digital) micrometer. This combined with a caliper's obvious advantages of external. internal, depth and step measurement makes it extremely interesting.
To the moderators I apologize if this sounds as if I'm trying to "sell" something - I'm not but it is why I preferred giving an answer by e-mail to anyone interested to avoid this situation!
I simply can't give a short answer and even this is lengthy although I've only scraped the surface
I have a geat deal of information on this and if you are really interested, then you'll have to e-mail me and I'll send it. <SNIP by Moderator>