It really comes down to your setup. Vicious dungeons allow you to prep what you want, choose your deity together with race and class, and get anything in the shops.
You can try multiple things, and exploit all kinds of synergys and weaknesses. Fail one? Try another.
Example: Dragon Isles. Definitely notot easy, and imo harder than most golds - but Berserker is especially effective on this map. Its also entirely possible to luck out and get Taurog, Pactmaker, and Dracul altogether on top of being a berserker. At this point, the dungeon turns into a fun little romp, easier than some silvers even.
Now, gold challenges are mostly about figuring out their trick, and what they give you is usually rather limited. They are mostly custom tailored to be doable, but not stompable. You don't get such wtf-syngerys nor do you get the same amount of deitys, shops, or items most of the time. You also can't prep for stuff like the dragonguard or the Indomitable. They are just plain hard.
Sometimes I wish Monk gold would give us shops. What would I give for martyr wraps... or a Whurrgarbl.
To put it short, I think vicious gets easier the more experience you have. Golds are rather fixed; you don't profit as much from your overall experience as you do in other dungeons.