In Las Vegas and Houston (I moved from Houston two years ago) they don't shoot it too much (lots shoot the 6.5x284), as the barrel life is nearly identical to the 6.5x284 (at least that is what teh one shooter that used it said). With both you can potentially play with Lapua brass, so that really isn't a deciding factor. It uses a bit less powder than the 284 case, so efficiency is better for the .260AI.
The only factor strongly favoring the 260AI, at least in my book, is that the loaded length is short enough that you can take one out of the chamber in a short action without having to pull teh bolt (not really possible with the 6.5x284 in any short action I've seen or tried - in my case a Neseka "K" - that currently shoots a straight .284 winchester for 1,000 yard F-Class and needs to pull the bolt to unchamber a loaded round...).
JeffVN
