Dim lights in dash

No, they are the same as far as how they dim the bulbs.
The experiences I have had with LED's is that they drop off suddenly when the voltage gets below a certain threshold, unlike a filament bulb.

If that is the case then I have been holding off changing for no apparant reason.

Ok, TB, I hear ya...but I hardly ever (read: never) run them that dim...usually on full brightness anyway, so it's really not a problem for me. Having brighter lamps was the reason I changed to them in the first place!