Any meaningful differences...

why do you ask?

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.

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.

To some extent, it depends on the resistors you choose. I use nude Vishays (VAR series) in all my controls, and I never use a ladder - prefer one resistor for each value step of the control. Rotary switch by Seiden SG. Makes the total pricey - 20x the price - but worth it on first class gear, like my DIY phono/pre.

But - I suspect that almost any rotary switch and almost any set of decent resistors will surpass the garden variety volume control in transparency and warmth i.e. lack of distortion. But be aware that there are those who don't believe that resistors make a difference. Even experts.

I suggest that you try it out - find the volume that you usually use, and determine the associated resistance - and install several types of resistor of that value in a rotary switch. Then make an informed choice.

I did that experiment with a Seiden SG, and found Vishay VAR to be best for me.

Hi fi fan seems you are expert DIY. Stock to stock do you notice huge difference  in transparency. For example top Primaluna preamps use Alps bluevelvet & some manufacturers  use stepped  attenuation  like Bat cj etc...

I like stepped attenuator because I can matching resistors for perfect channel balance and alter logarithmic curve to my liking. 

So you think stepped attentuator is more detailed vs a little bit of veiling disguised as warmth for high quality pots?

Can't remember if I had blue or black, preferred stepped,  natural and clean but sometimes 1 click is to low and 2 is too much, they also get dirty and need cleaning sometimes, installed a TKD and though it was a little sterile. No longer have the BAT but it had 99 step,  that was an awesome volume control.