Which booth would work best for me: AVB or SPB?

This really depends on what you are trying to achieve and your environment. For example if the goal is recording audio, voice over or singing and you are in a quiet place, then AVB is what you need. AVB ( Acoustical Vocal Booth) provides you acoustically treated room, that is removing echo and reverberations, and allow for clear quality audio recording.

But if you are in a noisy place and the goal is to block the outside noise, or vice versa if you are a drummer, musician who needs to prectice an instrument, or a singer, and the goal is to block the sound from getting out and disturbingthe neighbours, then you need the SPB booth. SPB booth blocks about 33 – 45 dB of sound, It also has a sound absorption blankets on the inside to deliver a reflection free acoiustically dead space.