Personally I prefer the powered versions becuase it gives more flexibility. As long as you are comfortable with your powered cabinet then that's fine but if for some reason you don't like it then your options are potentially more limited.
However the powered versions are also more expensive so...
You may find that the built in effects render your pedals unnecessary but if not your only other options are in front of the Kemper or as an output. The problem is depending on what you use the MP3 for, the effects maybe applied.
Thank you.
I'm Sorry, what do you mean? ↓↓
"The problem is depending on what you use the MP3 for, the effects maybe applied."
I will play through iPhone .