If the USB power is "good" the audio quality will be the same.
Often, connecting to a computer USB can cause ground loops and you get a significant increase in noise. Using a USB isolator (I use this one, for example,
https://www.olimex.com/Products/USB-Modules/USB-ISO/) breaks ground loops and ensures the audio is not affected.
Powering from a standalone USB supply (phone charger, etc) can work well too. But it depends on the charger -- Apple ones work well.
I haven't tried the Hobby Tronics converter, but I assume it will be ok -- it's powered from a standalone 5V PSU, so there shouldn't be any problems with noise/ground loops. I have used a similar product from Kenton and that works just fine when it powers the Wahoo.
