All quality frames are butted ( tubes thicker at ends for more strength) that I've ever heard of , and the turnip truck is miles down the road
If you mean welded when you say butted vs brazed -tough question many arguements for both, I'm NOT going into them since it may be a moot point since either process, when done right, produces a machine that will last a long time. (To my eye a Lugged frame is more beautiful)

I'd say most now favor welded frames since the welding techniques and the steels (such as self hardening at temperature Reynolds 853) have been much improved the last few years