You cannot even compare the precision mic to the instant indicator. The instant ind. does everything; headspace, seating depth, case length, bullet sorting. Also, it is press mounted, which makes for consistent readings each time. I have 3 of them, with 2 installed on my T-7 press right now.
I have an Instant Indicator in my T-7 as well......am very happy with it. Fast, easy, precise.
Precision Mic should not be compared to any other headspace tool if you ask me. It is slow and the bullet deating depth tool is just about worthless. I had one and gave it away.
The Hornady tool set that clamps to dial-caliper is also a good option. I am sure there are others that work well.
generally can be enough 1 indicator only and more bushings_ I work quite well with an Indicator only, (coming from a former 6,5 Swede set) and I use it with the .308 and 8mm.Mauser bushings_