Both Batman v Superman and Suicide Squad are terrible movies no doubt about it. I kind of flip flop on which one I think is worse. BvS was so convoluted it drove me up the wall, not to mention it's dark tone seemed very forced. Batman and Superman's motivations for fighting were both ridiculous, and of course, the Martha scene and that ending legit make me angry.
Suicide Squad was also bad, possibly worse, but in a different sort of way. This is one of the few movies I've seen that seems to take the fundamentals of films and really take them for granted. In BvS, there were about a million things going on and they are very poorly explained. In SS, it's almost the exact opposite. There's very little happening, and though it's not hard to understand, it's filled with a lot of random stuff that has no meaning, it's arguably not really a movie.
When it comes down to it, it's a competition between a really terrible movie and something that resembles a movie but barely counts as one. Choosing one or the other makes me want to die.