Both titles clearly dont have the comic book reader in mind so I wouldnt try evaluating them as decent literature
But as far as popularity? Zombie Tramp has had what? 17 titles overall? Its currently at issue #40
GFT has been around longer, has had over 130 (!) titles, its currently at vol II with over 130 books previous to that
A quick glance on eBay shows me a little over 1,000 items for zombie and over 14k for GFT
GFT produces alot more volume and grosses more money, its 1st issues are in the teens when it comes to print run, so that clearly isnt a draw for its collector-base
Yet with Zombie Tramp it is... Amazing