I have had a lot of trouble choosing a main character. Today my friend who mains Toon Link came over and we had a few games. He ***** my Olimar and Dedede and he barely beat my Wario and Bowser. I thought that was fair enough 'cause I'd been training with everyone at the same time whereas he'd already chosen his main and he could focus on him.
Then I pulled out the last character I'd been training with - Diddy. Even though I'd been using him less than all the others I thought it was still worth a try, so we had one last game, and to my very great surprise (but not yours, I'm sure, you could tell where this was heading from the end of the first paragraph), I won the match. So for now, I'm maining Diddy.
Honestly, I don't know what it is about Brawl that makes it so hard to choose my main. Back in melee I just fell in love with Yoshi straight away, then I moved on to Sheik and Marth when I got better. Maybe it's the fact that the character I most enjoy playing with is arguably the most hated alongside Snake (Hint - He has a cape and his name rhymes with Better Kite)
TL;DR version
I beat my friend with Diddy Kong and am going to try maining him for awhile.