Or you could get a good stainless steel barrel. They're a good middle of the road compromise for both types. Really decent life and usually better accuracy than a run of the mill lined barrel.
look for one that's chambered for either 5.56 or a wylde chamber if you want to use both .223 and 5.56 nato rounds. If the best accuracy is what you're looking for go with a match .223 chamber, though you'll only be able to shoot commercial .223 rounds and mil-surp will be out of the question.
The faster the twist (1:7) will be better suited for the heaviest rounds while a 1:9 will do just fine up to around the mid 60 gr ammo's and is the most common twist rate today.