Neck up or down?

[Warpt762x39]

In my research for potential firearms purchases for the (hopefully) near future, I decided that I want a bolt action rifle in .260 Remington.

It will only be for the range and as a personal challenge to squeeze every bit of accuracy out of each of the rifle, ammunition and myself.

I have noticed that .260 ammunition is kind of hard to come by and it is rather pricey. With that piece of information I have decided that the .260 bolt gun I buy will be fed only handloads.

After that decision I have found another small problem. .260 brass isn't all that common. Bullets are easy to find because of the 6.5x55mm Swedish Mauser rounds.

I have learned that the .260 Remington case is the same basic case as the .243 and .308 Winchesters. The new piece of info that I need is in regards to resizing brass.

Is it easier to neck down the .308 brass or neck up the .243 brass?

I can't recall ever reading any information on the pros and cons of necking either up or down. Any info would be greatly appreciated.

On a side note I had been researching a wildcat round with the same basic problem but in .25 caliber. Anybody have info on the .25 Souper?