Justin, don't over think the barrel. While there are differences in barrels, out in the field, most of those differences are minor. The difference between chrome and meloniting in accuracy might be as much as a half MOA. The difference in wear might be a couple thousand rounds, give or take. The differences in most profiles might be 2-4 ounces. The difference between a 16 and 20 inch barrel might be as much as 200 fps.
Buy a quality barrel with a 1:7 or 1:8 twist with a government, pencil, medium contour (medcon), lightweight or lighter weight contour made of 4140 CMV, 4150 CMV, 416 SS or 410 SS and you'll have good accuracy and will take a lot of money to pay for enough ammo to wear it out.
As for details, look for 1:7 or 1:8 twist, a lightweight, lighter weight or medcon profile. Chromelined or melonited doesn't matter very much and is more of a personal choice. Same thing with a 4150 or SS barrel.
The 1:7 or 1:7 will shoot almost anything well in the velocities the 223/5.56 will generate in barrel lengths from 10.5 to 20 inch.
The lightweight, lighter weight & government profile barrels all have about the same profile where it matters- near the chamber. The thickness of the barrel near the chamber matters when if comes to cooling and controlling heat. The extra thickness of the .gov profile, forward of the gas block, does little to contribute to controlling heat and adds useless weight. Some shooters like how it helps smooth swing when shooting at a moving target and helps settled the muzzle when shooting offhand.
If the barrel has M4 ramps, it's easier to find an upper to match. Few uppers are made with rifle ramp anymore.
If you get a quality barrel with 1:7 or 1:8 twist with M4 feed ramps in a profile and length that suits your needs, you'll get a barrel that works. (You'll hate a barrel you think is too heavy before you hate a barrel you think is too light.) The final thing is to make sure the gas port is the right size, which isn't a big deal. If the port is too small, it can be opened up. If it's too big, an SLR adjustable gas block will fix it.
FN barrels are an excellent choice