Well, its a funny story actually XD.
I started out as a Diddy main, and I would practice with my brother all the time. I hadn't been to a RL tournament at this point. Pretty soon I started to find out how the chaingrabs with Ice Climbers worked and I started to learn them. Around this time I started practicing on wifi aswell. Eventually I decided I would go 100% Ice Climbers, even though I didn't use them online because I couldn't chaingrab.
However...my brother started not enjoying fighting my Ice Climbers (I don't blame him XD) so my only practice left was Wifi... My only option was to revert back to Diddy to practice the game at all. So I learned Diddy all over again.
I eventually started going to real life tournaments and started liking the Ice Climbers again so I now use them in certain matchups that I don't like with Diddy.
I use Ice Climbers on:
-Metaknight
-Diddy
-Falco
-Dedede
-Sometimes Pikachu...depending on how confident I am feeling with Diddy.
-Olimar
-Kirby
-Sometims Wolf
I use Diddy on everyone else. I mainly just use Ice Climbers against those certain characters because of matchup experience. I know how to fight Metaknight with Ice Climbers, but I've never really practiced it with Diddy too much, so I just stick with what I know.
The best part about joint maining Ice Climbers and Diddy is that you never have to play dittos! Playing other Diddys as Ice Climbers is the most fun you will ever have. Instant throw naners back at them to combo into chaingrabs, being able to use the bananas and stuff overall helps the matchup sooo much, and I personally believe the matchup is 60:40 in favore of Ice Climbers if you have good banana control.
Basically I just enjoy playing Diddy and Ice Climbers, so I practice them both. It takes alot of practice because they are both pretty technical, but it is doable, and alot of fun