I've been doing a small science experiment for a science fair and I thought it would be good to post.
I left 5 burgers out on a table for 9 days and here are the results:
burger 1: McDonalds It never rotted at all!!!!!
burger 2 : Burger King It didn't rot instead it grew this icy substance all over the burger.
burger 3 : In and Out It rotted at day 5. It grew bumpy substances on it .
burger 4 : Smash Burger Same as burger 3, but grew common house mold.
burger 5 : Carls Jr. Same as 3 too, but instead it grew this greenish blue substance.
I also found out the size to the price
McDonalds has $1 burgers but they are mini like 1 inch and you can't even see the burger!!!!!
In and Out is probably best because it has quality, good and has real meat (cough cough), it also has a nice size burger and a cheap price (usually 3 or 4 dollars). Burger King is sorta a mix of both Mcdonalds and In and Out. Smash burger is a little bit bigger than In and Out but usually costs 5 or 6 bucks. Finally Carls Jr. was just like Burger king only bigger.
I think In and Out's burger is the best burger because it has so many good traits.
In and Outs burger after 6 days
All the burgers together

Carls Jr.
In and Out is top left
McDonalds is top right see teeny tiny little burger

Burger King

Smash burger

Carls Jr.

Poor Mcdonalds... :(