I currently carry a Glock 27 every day at work.  I want to get a good IWB holster that is easy on the finish.  I've heard that leather can wear off the finish more easily than a kydex-type holster and I've also heard the opposit.  It seems as though Kydex would be harder on the finish.  Who can settle this debate?

Not a very simple answer since there are many different types of leather holsters.

Basically, a holster is going to wear the finish on a gun where ever it repeatedly comes in contact.

With a kydex holster, since it's a rigid plastic, the finish wear is usually limited to small areas.  With Leather, is simply depends on how stiff the leather is.  Soft leather provides more contact which equates greater wear and tear on the finish.

ETA:  By "greater wear and tear" I mean the finish will wear over a larger area though it may take longer.

I don't think there is an answer to this debate.

Safariland makes kydex with a suede liner. http://www.safariland.com/DutyGear/concealment/holster.aspx

I can't answer the debate but I can put in my $.02.

I carry an M&P in a horsehide Super Tuck all day, every day, in the Florida heat and humidity; and since I retired,  a lot of that time is spent outdoors hiking and fishing in The Everglades.

There isn't any holster wear visible on either of my carry guns that I wear in the same hybrid horsehide/Kydex holster.

I'm used to significant amounts of visible holster wear on my older carry guns which I carried in leather holsters; although they were blued steel rather than polymer and  Melonite treated stainless like my M&Ps.

I'm of the belief that hybrid holsters are easier on guns than the all leather varieties.

Aww, come on! Let that carry gun show its experience!

I vote all Kydex, its thinner and more easily concealable and easier to reholster. Slightly less comfortable for some, just as comfortable for most.