How many pistols can you do?
Are you performing these as assistance to build strength or accessory to build muscle?
Up front both variations will benefit you. As long as you do it consistently and progress on it while working on your main lift you’ll see gains.
However as to which variation will “carry over” best to your squat it’d be the more constant tension pistol squat. This is because I more closely mimics your barbell squat which does have a relaxed pause at the bottom