The 8:00 rule

[Red Arremer]

After stocks, damage is the only way to properly determine something in-game. If you don't want to be in a disadvantage, pick your character better. Has noone read my posting?

Additionally, to quote what AlphaZealot said on the same topic in the SBR:

while it is true 90% on snake =/= the same effect at 90% on Kirby, the reality is that it is the same amount of damage and we need a way to have, at any point in time, a person in the lead. Percent is the only way to do that in match. More importantly, considering the rule is already in place and used at every single tournament, if the % lead were an actual problem for you in time outs then you should select your character more wisely. In other words that 90% of damage on Kirby means more than 90% on Snake is a weakness of Kirby that you should have considered when you selected the character.

I also noted there that if you wanted to do this by weight, you are bound to make a chart for every possible matchup.
Things you have to take into account for going by weight are, for example, if you play against a character that is bad or good at killing, what your survivability is (not weight only, considering the fact that G&W for instance can live FAR longer than characters that are heavier than him due to Bucket Brake), which options this character would've had in order to kill you, what the character's recovery ability is should one of them be offstage, what the other character's gimping abilities are should they have followed you, etc.