im really confused because that comic clearly has bad art and writing on purpose.
anyway, i think the writing/art debate is heavily influenced by situation. largely, in web comics, the art matters a lot more because of attention spans and all that - the chances i give a comic drop severely if the art is uncomfortable to look at, and skyrocket if i like the art. then again, i do follow a few comics where the writing trumped the art, so good writing can still save you. and if its BL the answer is neither art nor writing are important bc its BL and therefor unfairly favoured by creepy straight girls.
on the other hand, in print comics, ive read some comics with awful art - runaways and ultimate spiderman come to mind. the former had great writing, which made up for it, and the former was actually shit until about a volume before miles took over, but it was spiderman so it was successful.
theres also some comics with brilliant (or very fan-servicy) art that is so. badly. written. but people are happy to read them for artist loyalty, or just because theyre nice to look at.
tl;dr: while which will make you successful varies, and sometimes both can be bad and youll still be successful, on principle its important to keep both balanced and high quality