Why don't you create another character, play one as DK one as Sorc. The Twilight matriarch for me has been invaluable, it also has an ability to heal me. I would not completely rule out the idea of using a summoned aid.

I agree that playing both a sorc and a DK would be the best way to determine which feels best to you.

ESO isn't really like other MMOs where you choose a class and that locks you into one style of play/role. The class you pick is just a jumping off point. The DK you create could be completely different than the DK I created and they would probably both excel at different things.

Because of the above and the fact that everyone is different, no one can tell you what will be the most fun to play at endgame. I find the Templar to be the most fun to play at endgame, but you might hate it. Neither a sorc nor a dk are really going to be more powerful at endgame or have an easier time finding groups...Certain builds might be more powerful than others, and certain roles might have an easier time finding group (for example, a dk tank is probably going to have easier time finding a group than a dps sorc, just by virtue of being a tank), but your actual class is going to have a lot less to do with it.

Try them both, see what feels the most fun and what you play better. That is the class that should be your main character.

Thank you for your answers, I think I will bring a sorc to lvl 30 and choose then. Maybe I'll notice that sorc doesn't make as much fun as I thought while doing this. If not I'll choose the class that feels better. I hope none of them will get nerfed in the coming patches.