Do you/should you resize virgin brass? Advantages? Disadvantages?

Always. It also has to be chamferred inside and out. Some of the "virgin" brass I've gotten looked like it had been dropped on the floor, stepped on, and swept up before packing and shipping. Check the flash holes, too. I've found some really nasty boogers in them from time to time.

Craigster, I've always run the expander into the case mouth to get it round, but havent actually resized the case. Do you full-length resize?

I always full lenth size and trim at least to square up the mouths. Sean

Antlers,
I do it just like Lone Eagle. I also deburr the flash holes. Yeah, it's a pain in the ass but you only have to do it once. Thank God for small favors.

I AGREE WITH LONE EAGLE AND CRAIGSTER IT'S IMPORTANT TO FULL LENGTH RESIZE AND CHAMFER THE CASE MOUTHS. AFTER THAT I ALWAYS PUSH MY DECAPPING PIN THROUGH THE FLASH HOLE WHEN I FLARE THE CASE MOUTH. I'VE ONLY COME ACROSS 2 CASES THAT DIDN'T HAVE FLASH HOLES EVER BUT IT'S GOTTA BE CHECKED.

THE 2ND AMENDMENT PROTECTS US ALL........

I do more work prepping new brass then I do my fired brass. Check flash holes, primer pockets, fl resize, check necks and turn if needed, trim, and sort by weight. Once the brass has been fired in my gun I deprime, tumble, check primer pocket and flash hole and reload.

I agree that new brass needs to be run through the sizing die, but partial sizing is enough -- perhaps down as far as 3/4 of the way on the neck, but not far enough to possibly set the shoulder of an already minimal length case back further still! Equally important is chamfering a bevel on the inside of the neck. If there are burrs present, the outside of the neck rim should also be chamfered. Visually inspect flasholes, but unless they are obviously defective, any small burrs on the inside are insignificant to the performance of the load. However, if you're really anal-retentive and ENJOY searching out flashole burrs, the by all means, go ahead. I wouldn't want to deprive you of that satisfaction.

As the others mentioned, don't omit the chamfering step!!!

I just got back from the range, where I had taken my loading setup. I usually do all the case prep at home, then just weigh powder charges and seat at the range.

Well I forgot to chamfer the necks on 100 brand new brass, and I didn't have a tool with me, so I spent all day CRINGING as I shaved bits of jacket material off the bullets

Luckily, I worked up a nice load despite all that cringing.

PS I watch TV while priming, chamfering that sort of thing. You can get through 200 cases and not even notice it!