I think you'll find that between the 260, 6.5x47, and 6.5 Creedmoor they are all close. It'll come down to personal preference.
I have two rifles that I have shot in matches, both sniper matches and just banging steel.
1. Remington 5R MilSpec in 308 -- bone stock but its a shooter. It's in a AICS stock. The thumbhole on the AI is a love hate for some people... I recently switched to the Viper skins so it got rid of the thumbhole. I'm pushing the 175SMK's at 2725fps with Varget.
2. .260 Remington on a Remington action and Rock Creek barrel at 24". This sits in a Mcree stock. I am shooting the 140 Amax about 2810 fps with H4350. The 6.5 bullets fly so much better than the 30 cal bullets.
I'm having another 260 built on a Surgeon action and Krieger barrel that will sit in a McMillan A5 stock. I'm mostly likely going to turn the Remington 260 into a straight 284 Win since its the same bolt face and can be used on a Short action. I'll use the Mcree stock. It's probably going to have a 30" barrel and will push the 162 Amax well over 2950 with ease. The BC on the 175SMK is good too.
One more comment since you mentioned the 338 Lapua .... do yourself a favor and look at the 338 Edge. It can be built on a long action so it doesn't require the XL Lapua type action. The Edge will push the 300 SMK's over 2900 easily. Look for articles from Shawn Carlock. Ya I'm gonna build one of these too so I can shoot it at a mile.
You're more than welcome to lay down behind either rifle and send some rounds down range if you want to check them out.