In my opinion, the answer to this question is purely based on personal preference. Like you said, both of them are great and it's hard to pick a clear winner but let's do a little analysis before we decide.

MARVEL TV SHOWS

Marvel has the likes of Jessica Jones, Daredevil, Iron fist, Luke Cage(my personal favourite) and the defenders amongst others, holding down the forte for them on the small screen and they've done a really good job if you ask me. I'm a huge fan of Luke Cage and watching the devil of hell's kitchen beat up bad guys was and still is one of my favourite things to do. These shows are all exclusively on Netflix and this means that when a new season comes out, all I have to do is download all of it then binge watch all of them with friends over the weekend.

The characters in marvel shows are often very complex and you watch them as they grow and pass through different challenges that make and break them and with the exception of Daredevil, they don't really wear ridiculous looking costumes so that's a plus. It's not always happy and filled with smiles like DC shoes often are, it's down to earth and more realistic.

All the shows have good ratings on IMDb with the exception of iron fist which we all know is just trash. Their ratings ranged from 6.7 to 8.7 which by any standard is great.

DC TV SHOWS

Well DC brings the likes of The Flash, Supergirl, Legend of Tomorrow, Black lightning, Arrow and Constantine to the small screen and they haven't done bad for themselves, even going so far as to have frequent crossovers in what is now popularly referred to as the arrowverse. Their TV shows are more fictional than Marvel and so much less realistic, but I dare to say that they're also more exciting. You literally can't watch a single one of these shows without seeing at least one person get in to a fight or use their abilities in one way or another in any episode.

DC TV shows take the focus off reality itself and lets you dive into a fantasy world were just about anything is possible, you could say that they are to TV shows what marvel is to blockbuster movies. Yes, their characters are often very shallow and generally lack depth, but that doesn't change the fact that their shows are entertaining, I mean if I'm watching a show about superheroes then what I want to see are superheroes being super!!!

On IMDb I don't think they're big fans of DC TV shows because their ratings were pretty poor, ranging from 6.4 - 7.9, it's not too great but it's passable.

Well, finally, which is better?? Well I told you that it's based on personal preference and I personally have TV shows that I love and hate on both sides but in my opinion, the shows I enjoy more are DC TV shows, not because they're better, but because I just like the action in them. As far as storyline and depth goes, I've got to give it to Marvel, they're obviously the better story tellers and they have the more complex characters.