Someone gave me an old Starrett last word 0.001" indicator a few months ago. It's ok for some tight work, but otherwise, I use my interapid.
I have an interapid 0.0005" at home (flea market, $40, including extra tips and mounts), and use a B&S 0.0005" at work. The interapid is better (easier to setup), although there are times when I prefer the B&S dovetails on top of the indicator. The interapid has a different measuring angle (12* instead of 20* or 30*?), and a longer tip, which is nice for reaching spaces.
I think for a 0.00005" (50 millionths) indicator, I would prefer the B&S design. There are times when the long, round mitutoyo DTI's are nice for reaching confined spaces without extra-length tips.
I go for interapid #1, then B&S, then maybe Mitutoyo when picking test indicators for work.