Answer: I'm a fan of both those products. (I've got some Bick4 on order too)
Lexol is more penetrating but leaves more of a sticky residue in my experience. If the leather is old and has never been conditioned, I would use some Lexol first. If the leather is generally in good condition I would use Renovateur as its much nicer to work with IMO. I always use a layer of Renovateur on brand new shoes before anything else.
I end up using Lexol perhaps once a year and Reno about once a month.
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