4 vs. Artsy 9
4s and artsy 9s can be quite similar in their interests, demeanor, and wardrobe (especially ISP 9s). However, the main difference I've observed is that 9s tend to have a more 'nihilistic', earthy outlook on life. They'll often be more content with sensual activities like sex, drugs, partying, having fun, smoking cigs, eating junkfood, etc. than most intuitive 4s (especially if the 9 is sexual-first), or at least the latter is less likely to really emphasize those experiences. 9s also seem to put less of a filter on their tastes and self-expression, often listening to a variety of different music genres and associating themselves with all kinds of different people and subcultures. 4s are generally selective and high-maintenence to some extent, while the 9w8 aesthetic is characterized by more of a youthful virility or 'spunk'. Mellower, less impulsive 9s will still have more of a contentness and lack of emotional emphasis when compared to 4s.
On to the subject of music, many Sexual-9 songwriters have similar subject matter to 4s, but in some of the 9 lyrics I've listened to, you'll see more references to 'fucking' (and often drug use) than you'll see in 4 lyrics. 4 songwriters tend to gloss over sex completely, or only vaguely allude to it.
I'll write a description on 4 vs. 6w7, 4 vs. Sexual-3w4, and perhaps 4 vs 7, later.