As a fan of both Marvel and DC I don't find either roster particularly overwhelming (except for the multitude of Xmen and their history). I will say, however, that Marvel series are much more likely to get tied into a line wide event (much like how most current titles are being tied into Original Sin) and these events usually happen twice a year. This can get exhausting, but if you're not interested in the event, I think most writers do a good job to keep the tie-ins self-contained and still readable.
In terms of concepts, I find Marvel's cosmic stuff to be slightly more interesting. DC has some gold stuff like the New Gods and Apokolips and the 4th Dimension, but DC has been relying heaving on the Green Lantern line for its cosmic stories since the New 52. And I don't find the Green Lantern concept interesting at all. It's corny. The color spectrum that revitalized the Green Lantern title. Cheesy. I just can't get into it. Marvel's cosmic storytelling pulls from all sorts of stuff like the Inhumans, the Eternals, the Titans, Galactus, the Celestials, the Kree, the Shi'ar, the Badoon, the Skrulls, the Xandarians, the Spartax, the Nova Corps, the Guardians, the Negative Zone, Asgard and the Nine (now Ten!) Realms, and the Cosmic entities. Maybe I haven't read enough of DC's cosmic stuff, but Marvel's cosmic concepts and characters are more appealing to me than DC's.
That being said, I slightly prefer DC to Marvel. My favorite characters are DC characters (and usually female, which until recently, DC had a much better track record with than Marvel). But Marvel, in recent years, has been trying new artistic talent that is in stark contrast to the house style at DC (not that DC doesn't have exceptions to this house style). Pulido on She-Hulk, Aja on Hawkeye, Noto on Black Widow, Shalvey on Moon Knight, Tradd Moore on Ghost-Rider, Allred on Silver Surfer, Mike del Mundo on Elektra, Chris Samnee on Daredevil, Kaare Andrews on Iron Fist, Adrian Alphono on Ms. Marvel, Skottie Young on Rocket Raccoon. These artists all have unique and not stereotypical superhero art that makes for a visual diverse line-up of books. While DC has many great artists, I feel that DC is currently lacking in newer talent with unique approaches (although the new Batgirl artist and the artist for Gotham Academy are a step in the right direction).
tl; dr: I love both, but marginally prefer DC. I dislike the Lantern concept. I prefer Marvel cosmic. Marvel seems more interested in offering visually diverse titles than DC (for now).