I use 'em both, neetsfoot (real stuff, not the petrol goo) on the underside of especially-dry saddles that I don't want to use a baseball bat on to soften, and proofide on the top surface to (in essence) waterproof and also to seal any cracking etc. You think Proofide soakes up fast into the non-finished (rough) leather? I just finished treating a Brooks Pro on a 72-ish PX10 that was so dry it soaked up almost 4 ounces of neetsfoot on the underside! Thing looks good after three thin coats of proofide applied with a full sun-drenched soak-it-in day between each.
Get the real neetsfoot at a tack shop or place like Murdochs. 40 years ago I'd get it at the drug store (after they checked to see if it was a controlled substance?!?!?!)
I forgot about snoseal. THAT is good stuff too.
One final caveat: I NEVER use proofide (or snoseal) on the UNDERSIDE of a saddle unless it is severely severely dry. Think I read nasty talk about that here. Neetsfoot works better and can be brushed on evenly and doesn't seal the leather (I hear that still allows it to "breathe"...how many other dead animal parts you know that need to "breathe"?)
Dale Phelps,
Montagna lunga scalatore Colorado USA