>>14293938I like to do a bit of both, and I follow a set of team building rules:
Keep the starter on the team
No two pokemon with the same type
Never use a pokemon I've used before
Always use the pseudolegendary of the gen on the first run
No legendaries
Give preference to pokemon released in the current gen, but definitely not an absolute rule
Apart from that, I use the pokemon I like - I usually go for pokemon based on aesthetics, ability, movepool, and cool typing combinations
The end result is I get a team of all new bros who I genuinely really like, and the team is usually something I can take onto pokemon showdown and play with some success in OU.