Which reminds me...
Different*, immediately*, a lot*, which*.
A lazy person with two characters will be lazy with one. An uncreative person with two characters will be uncreative with one.
It makes little to no difference whatsoever about how many characters you play. It's about how you play them and how much time and motivation you invest in them. Which is why I keep it to two or three as a safe maximum. Beyond that, and then you risk not having enough time to really flesh out your characters.
So. As I said above, reworded.
1's a solo, 2's a duo, 3's a party, 4's too much.
Note: The only exception I can think of is a nation RP. In which case, well, yeah.
Also, you're right, it is a personal choice!... That should be up to the individual role player to make for themselves, like if they want to weave in romance options with their character(s). ;p