I confess to liking both.
I had read the Marvel Conan as a kid. I remember owning a book which was "
The Twilight of the Grim Grey God" - probably Conan the Barbarian #3. Drawn by Barry Windsor Smith who used to draw a very young lithe Conan. As a kid, I read that book many many times and I tend to think of the story as being Howard-esque. I think it might have been a pastiche or whatever Conan/REH biographers term the thing - with some ideas taken from another REH story and reworked into a Conan story but it greatly appealed to me. The whole idea of Gods who "pass from this world" when their followers are no more, really made sense to me as I was getting exposed to multiple myths/gods (Greeks, Romans etc at that time).
Barry Windsor-Smith's Conan work is pretty great. There are a couple of really great collections - Conan: The Barry Windsor Smith Chronicles -
Parts 1 and
2 that you can get from Amazon or if financially-challenged (in my case) from your friendly neighborhood library (utilize the Inter Library Loan mechanism if your library doesn't have it).
John Buscema's Conan *is* Conan to me. I never saw the Frazetta covers. He came on as the artist after Barry Windsor Smith left. He had been the primary person in contention as the artist when Marvel was starting Conan per Roy Thomas except that he was too pricey an artist for what Stan Lee had originally planned for this. The way Buscema drew Conan is how I truly imagine Conan in my head - not Arnold

- who except for the accent made a pretty decent Conan - tho' there's something to be said for Arnold's Conan's delivery of the following quote
Mongol General: Hao! Dai ye! We won again! This is good, but what is best in life?
Mongol: The open steppe, fleet horse, falcons at your wrist, and the wind in your hair.
Mongol General: Wrong! Conan! What is best in life?
Conan: To crush your enemies, see them driven before you, and to hear the lamentation of their women.
Mongol General: That is good! That is good.
Dark Horse's Conan visually doesn't appeal to me as much as BWS' Conan and definitely doesn't come close to Buscema's Conan. However, they tried to make him more "realistic" and not have him be his usual bare-chested self - a different approach. I liked the writing quite a bit. I liked how they set up the story within a story aspect which is vaguely Arabian Nights and yet seems to be tying up in the future. (I sure hope that the tie-up happens and Dark Horse doesn't end up cancelling Conan without us ever learning more about the Vizier (who we all suspect to be... <no spoilers> ) and if... <no spoilers again>).
It's well-written and tries to lay a structure to Conan. When REH wrote Conan, he wrote about several episodes at different times in Conan's life and what they are trying to do is string it into a coherent storyline with their own "inventions" filling the blanks until they get a chance to do an adaptation of the REH story.
So - yes, I do like Dark Horse and I like their story telling. I started liking Cary Nord's watercolor approach too after a bit. They did a few adaptations quite well - the Gunderman storyline was a splendid addition to Conan as is their take on Jenna. It works better for me in the Dark Horse comics than in the old Marvel comics. However the tower of the elephant is still more splendid in Marvel.
So - in a sense - I like the old and I like the new.
What I don't like is Jason Momoa as Conan.
But that's a whole another post.