I put this same reply in another thread a while back.
http://www.turbobuick.com/forums/turbo-lounge/340394-micrometers.html
It depends on what you want to measure.
If your just measuring bearing clearances when assembling your motor, you don't need expensive mics. Your only measuring the difference between the crank OD and the bearing ID and you'll be using the same mic for both. Any mic is going to be good inside that range. Enco has good deals on import mics that would work fine here.
If your measuring something and need to compare it to something measured with with another mic, you need expensive mics. I prefer Mitutoyo and Starrett.
A dial bore gauge is going to be expensive even if you buy an import. If your competent with measuring tools, you might be able to get away with telescoping gauges, but they take "the touch" to use accurately.
I have fully stocked general machine/ fab shop at my house and I don't own a dial bore gauge. It's just not cost effective to have one for the very few times I would use them. The other problem is if you find a clearance out of spec, can you fix it? Better yet, if you find something out of spec, do you trust your measurements? I would much rather spend that extra money for a quality machine shop to cut, grind and hone my parts to size and assemble everything.