My holy grail black liner is the Giorgio Armani Eyes to Kill Waterproof liner. It's the blackest black and longest wearing liner that I own. However, when I received the Urban Decay 24/7 Glide On Eye Pencil in Perversion for my birthday I thought it was a great opportunity to compare the two.
Urban Decay's Perversion is formulated to be even more black than their Zero liner. For me Zero is more of a grey black and Perversion is a true, inky black that is very comparable to the Armani liner. Although I still prefer the waterproof formula of the Giorgio Armani liner, Perversion is a close second. The Urban Decay Glide On Pencils wear well when set with a powder, so I don't see much transfer or smudging after 8+ hours of wear.
My thoughts? I'm enjoying the Perversion liner as an alternative for the Giorgio Armani Eyes to Kill, especially since Urban Decay's liner is much more affordable.