John, thanks for providing the additional info. While obviously many variables are involved, some of them predictable and some not, IMO chances are that the overriding consideration will be conformance to the load capacitance recommendation for the AT95. Failure to do that is likely to have adverse effects in the upper treble region. I see that most or all of the available versions of the AT95, which are distinguished by lettered suffixes, are recommended to be loaded with 100 to 200 pf of capacitance.
The total capacitance seen by the cartridge will be the sum of the input capacitance of the phono stage, the capacitance of the interconnect cable between the turntable and the phono stage, the capacitance of the tonearm wiring and other internal wiring in the turntable between the cartridge and the turntable's connectors, and the capacitance of all of the associated connectors.
Unfortunately the input capacitance of the phono stage appears to be unspecified, and the capacitance per unit length of your MAC cables also appears to be unspecified. However, it is likely that the input capacitance of the phono stage will be a substantial fraction of 100 pf, and possibly 100 pf or even more. Odds are you will therefore want to use between the turntable and the phono stage whichever of the two cables has the lowest total capacitance. Total capacitance equals the capacitance per unit length of the particular cable type multiplied by the length of the cable.
It would be a good idea to contact MAC and see if they can tell you what the capacitance per unit length of each cable is. If the capacitance of both cables turns out to be too high, consider Blue Jeans LC-1
, which is very inexpensive and has very low capacitance.
Also, I see that the Velvet cable is explicitly described as being shielded, while the more expensive Ultrasilver's description makes no reference to shielding. Chances are it will be more important to have good shielding in a cable that is conducting low-level phono cartridge signals than the higher level signals that exist between the phono stage and the line-level preamp.
And when and if you do a listening comparison of both configurations, focus on the treble in particular. It's hard to say for sure without complete technical data on the cartridge, but most likely too much capacitance in the turntable to phono stage interconnect will result in an undesirable frequency response peak in the top octave. See this paper