Tough question to answer as anyone who has done both would have the experience of the second one tainted by the first. No one could give you a neutral/objective comparison of the experiences.

I did it in person. Sitting in a room full of your peers answering questions is priceless. It's hard to BS a room full of people, much less Albie. I did mine with my CO and another pilot from my squadron listening. Also, listening to others helps you come up with new/better/different ideas for your own answers.

If you have the time, do it in person and use the phone prep to refresh. If you are pressed for time (interview before the next in-person session), make the call.