Depends on your personal preference. The 24" bbl will add approx. 50-60 fps to the given cartridge load. If hunting in brush, most people prefer the shorter length. Where I hunt (open mountain areas) the longer bbl works best. If you do a lot of hiking and hill climbing, then the shorter bbl will save a fraction of weight. As far as accuracy, don't think there's a whit of difference between them.
It's mostly a matter of personal choice. I have a 24" barrelled 30-06 that I have used for about ten years now, and I like it fine. I hunt some pretty thick country and have not had problems getting it through the brush. I do wish my rifle was a little lighter, since I'm not in great shape and the hills get steeper as I age, but it's not bad - a shade over 8 lbs with scope and sling.
I've given this advice over and over - pick whatever rifle feels the best and don't worry too much about details like barrel length.
find the rifle you like, that fits you, and it will answer your question for you. Most factory rifles don't come in the same configuration and caliber with a choice in barrel length. The velocity difference is a non concern with the two lengths you mention. The accuracy difference would likely be nill. There is a a bit of evidence that a shorter barrel actually has more accuracy potential all else being equal. That said, in a factory rifle, I wouldn't let it influence my decision in any way.
I'm a big fan of the 'ole 06,and have shot 'em alot. Mine all have 24" barrels, and I prefer them that way. I also believe there is an "ideal" barrel length for most cartridges, based on case capacity to bore ratio(regardless of case shape.)
But don't get too hung up on any specific barrel length especially in regards to a velocity standpoint. A 50-75 fps difference between 2" of barrel length is somewhat inconsequential and could be the difference between two barrels of the same length. this is sometimes refered to as a "fast" or 'slow" barrel. Variations in internal chamber or barrel dimensions, bore finish, etc. can make one rifle 'fast' and an identical rifle 'slow' when using the same ammunition.
One example in print lies in the Speer reloading manual vol.12 page 434. "Why Ballisticans Get Gray" by Dave Andrews. This touches on some of the differences one can encounter. Although the example is primarily revolvers it is applicable to rifles as well.
Re-stating some of the best advice already here, is to find a rifle that fits you. I prefer a longer rifle with barrels of 24-26" and a lengthof pull around 14"+. But, I'm a full 6'4" and 290 lbs. My wife is 5'7" stoutly built Cajun lady who prefers barrels in the 22"-24" area and lop's around 12.5". Now my brother in-laws wife is 5'2" and 95 lbs. with a pocket full of rocks! Her rifle is a 18.5 "barreled 12" lop'ed 308.
The differences here are obvious. Stature and build play an important part in how rifles fits. My wife, although not tall, has enough strength and arm length to handle most factory rifles by just installing a thinner recoil pad. ( No, my wife isn't a gorilla, but she does intimidate most men as her favorite rifle is a 338 Winchester!) If your rifle fits you, your preformance will be better than just barrel length alone.
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