Phew! Just made it! It's always an uphill battle trying to suss out certain things in the TV Tropes site.
Day 02 - Your favourite main character:
It is actually surprisingly difficult to choose between Sherlock and John.
Sad to say, but I fear I am quite shallow when it comes to favorite characters in my visual media. I do have favorite tropes (which I will discuss in a bit), but I also seem to gravitate towards those I find physically attractive. However, I can honestly say, I don't find either very attractive at all. So in that regard they are even.
As far as character typing, I have a few favorites that I tend towards:
the Everyman,
the Trickster,
the Ace, and
the Pragmatic Hero.
Now, from what I can tell, neither John nor Sherlock embody the Trickster in any way (Moriarty on the other hand...), so that's right out. And while John is clearly the Everyman and Sherlock the Ace, I can see both as the Pragmatic Hero.
So that's 2 and 2.
Outside of tropes, both characters are fleshed out and quite multidimensional. John, who seems like nothing more than the bloke next door until suddenly he's the hardened war veteran, the paladin, the doctor (implying intelligence and skill) and then in another twist is also apparently the conscience, the interpreter and the best friend imaginable. Needless to say, Watson has a lot of hats. Sherlock less so, but is no less faceted for all that. He is the scientist, the detective and the outsider. The first two speak for themselves, the third might need some extrapolation. Unlike John, where what he does illustrates the character, Sherlock's character is determined by how he thinks and how the viewers think he thinks. While nothing is laid out in black and white nor stated in an official medical capacity, Sherlock has aspects of the genius, the sociopath, the psychopath, the narcissist, the autistic, the asexual, the bullied, the immature and the just plain clueless. That is a lot to hide under one roof even if only bits and pieces apply.
Score another point for both.
Last point of contention? Real world applications. John Watson, by far, would be the more easier person to get along with in real life. He'd be reliable and fun, knowing when it was appropriate to go off on adventures and when to let real life take over. I admire and empathize with his sense of pride and duty. I understand his brokenness (not the military aspects but still). Sherlock would be a pain in the tukhus, no question, but I've found from personal experience that access to such sheer intelligence more than make up for that flaw. And at the risk of revealing too much about myself, I can relate quite well (though on a significantly lesser scale) with the genius, sociopathy and asexuality portrayed. I believe my sister will claim I have the arrogance down pat at least.
I think I probably knew right from the beginning, that I wouldn't be able to choose between these two characters. They are both favorites, though for different reasons. I hope you don't take it as a cop out.