While they both play completely different, and there is no accounting for taste...the Telltale one was made better in just about every way. The one from Activision was nothing more than a quick cash-grab. The game was in development for like 8-months (no joke)...and it shows.
The Activision WD game could've been so much better, as it has some good ideas, but it screams rush-job throughout, and so it is very sloppy. Not to mention it lasts roughly 5-hours long. And it is getting hammered in Reviews (rightfully so).
But I want to be completely fair... The Telltale WD game is more accurate to the comic, whereas the Activision WD game is more accurate to the tv show. The comic & the tv show do not actually follow the same formula. They have similarities, but they also have vast differences. So if you are a big fan of the comic, then pick-up the Telltale version...and if you are a fan of the tv show, then pick up the Activision version. (just expect some sloppy mechanics, very short campaign, & plenty of bugs in the Activision game).