The round neck resonator will allow the instrument to be played like a traditional guitar while also still being able to lay the instrument flat for true lap style slide playing. Whereas the square neck is only designed for flat lap style slide playing. If your goal is strictly “lap steel” type slide playing, go with the square neck. It will be the purer experience. If you want to play traditional guitar techniques in a standard playing position in addition to some slide work, the round neck is a must.
