Why do we choose what we choose in competitive play?

Ultimately, what made me pick Shulk over Ike in Smash at the end was merely, that he is difficult to play and because I found his Monado arts pretty interesting. Originally, I went with Ike, just because I saw some Youtuber playing with him and even now I like randomly picking Ike, though, I'd still pick Shulk most of the time, because of his interesting playstyle.
Back when I played Dissidia I used to play a bunch of characters...

I was browsing through TV Tropes the other day. To be exact, I clicked through random video game related tags, because I wanted to waste a little bit of time. And while I was looking for interesting topics, I stopped when they brought up the phrase "Fun Through Dedication", something that I found particularly interesting. So interesting that I thought talking about it would be a good idea.

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Now, first of all: what does "Fun Through Dedication"...