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.