I’ve only ever used the mechanical type (Starrett) edge finder. It does fine for my small, cast model kits.

Here is a good 7 min comparision of Mechanical v Laser (ball end)  ….. Better than a mechanical edge finder? –

TLDR –

Mechanical – cheap (£25 or so), no battery, small (about 100 mm long), accuracy to about 0.025mm (one or two thou”), slightly more difficult to use but still easy enough.

Laser – 5x more expensive, much longer in the Z axis, very accurate and easy to use, less prone to finding burred edges, battery powered.

There are also finders using actual lasers but one has to eyeball where the laser beam falls. Those seem, to me, a bit more hit-or-miss (?) but I have no experience of them.

Ches

Edit: The ‘laser ball end’ I referenced may not actually use a laser…it’s more of an electronic device…but looks interesting nonetheless 😉

Ches, that is just an electronic find. Lights up when it contacts metal and completes the circuit.

He is showing quite a large one, I have a smaller 1/2″ shank PEC brand one which is no bigger than the mechanical one he shows so no downsides. Battery tends to last 5-6 years

Electronic Edge Finders

I just hold a metal block of known size against plastic and that works fine so long as part of the block is touching teh vice jaws, etc.

SDA laser edge finders occasionally appear on eBay for around £30-40