Which do you prefer, a 24" barrel or a 20". I am trying to decide but I'm stuck.

 What do you intend this rifle to be used for, and is it an AR?

 Chuck

it is an ar. mostly will use it for target and varmit hunting. I want to know if a 24" is "too long" and if there is a big accuracy difference between the barrels, both are bull barrels.

 Not too long I think, I prefer 20" barrels myself, but that is personal preference.
 As far as accuracy is concerned, I think that accuracy lies in the barrel and its manufacturer more than in the length.
 Get a barrel from a reputable manufacturer, and get it in the length that will please you.
 Some people say that the real long bull barrels will put undue stress on an AR reciever.
This is due to so much weight being suspended so far forward.
 I have seen 16 barreled ARs that will shoot bug hole groups at 100 yds, and 20" rifles that will not group in a coffee can at the same yardage.

 Chuck

24" come-on man its a size thing dont let anybody tell you different. Any longer you should be a porn star!

hg112: I like the 24" but from 100-200yds. hard rub, If you shooting under 200yds. stick with 16"-20", but 400yds-on the 24" shines.

One of the biggest arguments I would have here, simply because you said that they were both "bull barrels", would be a weight concern.  If you're only shooting benchrest, bipod, prone etc, then a 24" will suit you nicely.  However, if you EVER plan on going offhand with that badboy, you better have arms the size of pythons to efficiently hold a 24" bull for an extended period of time.  

I'm not ripped, but I'm a fairly well built person, and I can't hold my uncle's 24" HBAR for more than 2-3 minutes without having to give that left arm a rest.  Just something to chew on...