Does a “good mix” have to be beatmatched for you? If yes, then I would say anything with a live drummer.
Otherwise it really depends. In Hip-Hop, a simple cut can sound really good, while extensive scratching in the wrong places can destroy a mix. One is really simple to execute while the other is technically more advanced. Does that make Hip-Hop in generall harder or easier to mix?
From my own experience with deep and tech house, it’s not about beatmatching but to avoid clashing melodies via track selecton and EQing. Technically it’s easy to get a decent sounding mix when you stick to percussion-only intro/outro mixing, but it’s up to you if you define this as “well mixed”.
So, every genre has basic and advanced mixing techniques, both can sound good. However, I don’t really get the intention of the question; either you’re trying to decide which genre to play based on the difficulty of the mixing, what should never be an argument. The other option is, that this will end with people arguing that their genre is easier to mix than something someone else plays.
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