The advantage of the Precision Mic and the caliper gages made by Hornady and Sinclair is you get to use them to detect small differences you can control with your die setup. The Wilson gage is really just pass/fail case length gage that insures the neck is trimmed enough at one end and that the case headspace length is within SAAMI specs so it will fit into any SAAMI compliant chamber. The other gages allow you to take a case fired in your own chamber and set your sizing die so it only moves the shoulder back a thousandth or two, which means it will still fit in your own chamber just fine, though it might not fit in someone else's chamber if their chamber is shorter. But that minimum amount of sizing is all you need for your gun, and it tends to result in longer case life, because you work the brass less, but more importantly tends to give you better precision (smaller groups).
But there's more. A separate thimble, in the case of the Precision Mic, and separate inserts, in the case of the Hornady and Sinclair adapters, let you measure length from the case head to the a point on the bullet ogive that is close to the diameter at which the bullet actually contacts the rifling lands in the rifle. The Precision Mic come with a special gage for finding how far the lands are from the breech in your rifle. Hornady makes a separately available gage for this purpose called the overall length gauge that works with a caliper-specific adapter. Sinclair makes a separate seating depth gage that works independently of the caliper gage.
The main differences between the Hornady and Sinclair gage caliper adapters (Hornady calls its adapter the gage "body") is that the Hornady adapter slot for the caliper jaws is slightly offset from the centerline to make it work with the caliper laid into their overall length gage, while the Sinclair adapter jaw slot is centered on the caliper jaw, making it slightly easier to use independently of a gage. The Hornady gage uses aluminum inserts, one set for case headspace and one set for bullet ogive contact. The Sinclair uses stainless adapters for bullet ogive contact that are cut with a chamber reamer, which lets it sit further down on the ogive and closer to the actual bullet contact position with the throat.
Sinclair makes no case headspace inserts for their adapter, but the inserts are interchangeable in the two adapters, so you can use the Hornady case headspace inserts in the Sinclair adapter, and the Sinclair stainless inserts in the Hornady adapter.
If you own neither, and want to make the measurements they can make and want to go the caliper adapter route rather than the RCBS Precision Mic route, I think the best caliper combination to start with is to get the
Hornady case gage kit with body and buy the
Sinclair bullet inserts for your calibers and the
Hornady Overall Gage (straight for bolt guns only or curved for both closed rear receiver semi-autos and bolt guns) and a case adapter for your chambering. The last two items are for determining bullet seating depths.
Bottom line, you need to know what information you want and what you want it for. Most precision loaders want all the gage information they can get in order to control their loads in more detail. But if you just want to be sure you are producing case lengths that fit all guns, the Wilson does fine.