I recently aquired an AR with a 24 inch barrel.  My question is what are the pros and cons of this length barrel.  

Thanks.
Bill

Pros: You can hit a homerun with it
Cons: Sumbitch is heavy and long, so practical use is probably restricted to a bench.

FWIW, someday I plan to build a side charging precison rifle with a 24" bbl. Strictly for bench shooting.

Yeah I noticed the weight as soon as i picked it up.  It FEELS a good 2-3 pounds heavier than my 16 inch barreled AR.  I asked my uncle why he went with the 24 inch barrel and his reply was " Cause it'll be more accurate when I take it hunting."  Now seeing as Delaware doesn't allow hunting with rifles (exception is .22lr for squirrel) I don't know what or where he was planning on hunting with it.  And he zeroed his 3-9X scope at 30 yards.

Higher velocity
It's unwieldy for some

I like it for shooting off a bi-pod or sand bags the weight works to your advantage when shooting makes for very light recoil.

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my varmint gun is a 24 inch barreled bull upper on a DPMS stainless lower.

Have carried it walking on jack rabbit shoots with no problems.   Shoots from the standing just fine and with a sitting bipod I can hit a sitting position and take some pretty quick shots as well.   Have jumped Ca. jack rabbits about 25 yards from me and had them dead by the time they hit about 300 yards.

Weight is all in your mind.   Have used the same rifle for 3 gun, is it the fastest?   No, but it doesn't have any recoil either at nearly 14 pounds unloaded.

Cons:
1. they're heavy (you will need a sling if you plan on carrying it past the bench)
2. they're long  (you may poke your eye out)
3. they attract attention (you may have justify it to purists who think 16"  is all anyone needs)

Pros:
1. they're heavy (takes longer to heat up / greater surface area for cooling)
2. they're long (increased velocity flattens tragectory and increases effective range)
3. they attract attention (show' em your 1/2" groups and say it's just not a good day)
4. they're dead-sexy!