I am trying decide if I should main a warlock or a DK for SL.
I like to WPVP and solo old raid content and do BG’s. I dont really mind if its ranged or melee and I would dps only (not looking to tank).
Would warlock be a good fit for that criteria or would DK be a better fit?
Thanks in advance!
I can’t speak much for Dk since I don’t really like the class, but warlocks are super fun. I’m leveling my 2nd on my new realm.
For solo content you won’t have a problem - you’ve got plenty of self-healing, shields plus a pet tank.
WPvp? Omg, I love Chaos bolting from afar. You can delete people easily.
DK is really fun.
Warlocks are really fun.
I see your dilemma. I would pick DK personally due to tanking old content raids quicker. Up to you
Have you played a clothy before? It can be jarring at first, learning how to think about positioning and portals/circles so your not a melee target dummy.
Having said that, once you get good and crafty with using the toolkit, locks are amazing fel-fun.
Although, I’m clearly biased having played this toon since 06. 
Any ranged dps is easier to play than any melee. Warlocks have a tank pet so it makes it even easier to play solo.
DKs are great fun but for the aspects of the game you mention, you’re better off with a warlock imo.
For WPvP, I would chose the Death Knight over Warlock many times.
Warlock PvP is pretty reliant on being prepared which is pretty easy in organized PvP like BGs and Arena, rated or unrated, but pretty difficult in non-organized PvP. If your Circle and Gateway aren’t up then most melee specs will shut you down.
Right now, if someone jumps you in the world as a Warlock, it’s a tough fight assuming equal skill/gear. If you get the jump on them then it’s pretty much an easy fight regardless of class/spec. You’re probably starting at max range, have Circle and maybe Gateway up and may even have the correct pet for the fight. If you’re Afflic, you’ll probably have every DoT on them before they even realize it.
If someone gets the jump on you in the world as an unholy DK, you just pop army and laugh as your pets decimate them and you heal any damage you take with Death Strike/Licheborne and Death Coil. They’re more likely to run (and escape) from you than kill you with every CD available… Unless they’re a Druid, maybe.
Their more similar then you think and both have a high skill ceiling if your thinking of Unholy/Affliction. Both are looking to be looking good in Shadowlands so can’t go wrong with either. Comes down to class fantasy, aesthetics, and range vs melee.