Proofide is mostly an oil dressing with a bit of wax thrown in. Pure neatsfoot is an oil dressing without the wax. Neither will hurt your saddle if you don't overuse them.

I've had great luck using two coats of baseball glove oil (neatsfoot with lanolin added) to assist with breaking in a B-17. Afterward, it was slightly softer than another B-17 with just Proofide applied and noticeably more comfortable.