There is some absolute misinformation here.
IF you KO your opponent (1st MUST condition!)
You get 2*X extra points at the end of the battle, where X is the nuber of pillz that you did NOT use.
IN TOURNAMENTS there is a maximum of 5 (five) extra points this way. Therefore it does not make sense to save more than 3 pillz since 3*2=6 => 5 and every higher amount of pillz will equally net only 5 points. (Whereas 2 pillz would net 4 points and 1 pill 2 points.)
This is all found in the manual, btw. You know... it is there to be read.
http://www.urban-rivals.com/game/rules.php?show=table [near the end]
Mhm... talking of "it is written there..." I am pretty sure about the 5 max in tournaments but it is not written there. Possibly sb. should add it. (Or did I confuse things with the tournament max?)
From the "JOIN ROOM" page:
[coup picture] Take note that in this room, during all daily tournaments, the number of bonus points awarded for a character levelling up will be limited to 0 pts, KO bonus are also limited to 2 pts. Finally, everybody must be visible during a tournament.
However I think that it was 5 points before and even more before that. When I started playing here I used to get up to 30-40 points by KOing fast and keeping lots of pillz