It really depends on what repertoire one wants to play.
Normally I would recommend the Eb tuning, to have also some flats.
Myself at the moment I play a lot of Irish music and prefer the E´s and A´s
goodsounding, so I tuned my harp in F leaving one flat possible. Also because playing in sessions uses the strings more than solo playing; my strings always break where levers are used.
Are there lever harps where the use of a lever does not affect the quality of the sound???