UPjeeper, if you want to hit prairie poodles in the 300-400 yard range with a .223 AR, best results will come if you use a more varmint-type barrel (longer) in the 22-26" range, with a faster twist to shoot the heavier bullets, which buck wind better. The barrel need not be heavy, but that would certainly help in holding steady and soaking up the heat from any "ranging shots" (misses) you might make before you hit (trust me, you WILL be making "ranging shots" at that range!).
Now before anybody jumps in and says they've killed hundreds of sod poodles with a 14" twist 16" barrel and 55-grain pills (which will certainly work), I said 'best results'! Longer barrels get a little more velocity out of the round, and heavier bullets buck the wind better.
My prairie-dog shooting partner has an AR with a stainless fluted 1-8" twist 26" barrel made by Mark Chanlyn. He shoots the 60-gr. Vmax (which only needs a 1-12" twist in a .223) and I have observed many of his hits out to a laser-ranged quarter mile. That distance is pushing it a bit for those lighter bullets out here in windy Colorado though.
Go with the longer heavier barrel and an 8" twist and you'll be able to shoot bullets up to the 80-grain Sierra Matchking or 75-grain Hornady A-Max for long windy shots, yet still be able to shoot the 55's or 60's if you like. The 60, in the V-Max (Hornady) or hollowpoint (Hornady and Sierra) is a darn good all-around weight for shooting out to 400 if the wind isn't too horrible. I've ruined many a rat's day with the 60 V-Max. Now if only I could convince Steve Hornady to make a 70-grain boattail V-Max or A-Max, that would be perfect for me (I've tried, and he won't...yet).
Oh by the way...on the original topic, it seems mostly a matter of taste. AR's are more pricey but more versatile, and generally heavier. Bolt guns are trimmer and can be had very light indeed (Rem. Model 7, Browning A-Bolt Micro).
Handling qualities are very different. Me, I hate the way an AR feels, and love a trim light bolt gun. But, it's hard to beat the efficiency, accuracy, and versatility of the AR.