Any meaningful differences...

I do most of my listening to a pretty good quality desktop audio system these days, with or without headphones. One of my headphone amp/preamps, the Violectric V281, is a very fine system preamp, as good as any I used in the big 2-channel system days. My version is the top/ultimate model with a 100 step, remote controlled pot (made in house by Violectric). Others that own this unit get it w/the standard Alps pot. I have not personally compared the units, but those who have typically say the following things:

• With the non-stepped pot, the V281 sounds very good--with none of the minor artifacts of the Violectric stepped pot (minor switching noise)
• But with the stepped-pot, the V281 sounds noticeably better, with more transparency, resolution, and slightly greater dynamics

I suspect well designed & made stepped pots will always beat a non-stepped pot, so long as there are sufficient steps to provide granular volume control. I had one preamp w/stepped pot that had just 22 steps, and it drove me nuts because, due to gain issues IMS at that time, only the bottom 3-4 steps were practical to use. I have another violectric headphone amp (not preamp) w/an Alps 43-step unit. I find 43 steps sorta/kinda sufficient, though with extremely efficient, low impedance headphones (translation: loud as hell), it, too, really doesn't have enough steps for practical use.

Pots wear and log pots don't track particularly well.

The problem with stepped pots in passive preamps is they need to be mated to the driven device. When the input impedance changes, so does the taper. If the R values are adjusted to provide accurate steps with a given impedance, 1db steps are fine. Adjust for amp gain and speaker efficiency as necessary. See http://ielogical.com/assets/Audio/PassiveLC1.png for how to adjust. PM if you need more assistance.

why do you ask?