Re: Lapua brass
You'll only be able to get Lapua brass for your 243. They don't make 300 win mag brass. There is some 300 win mag brass out there with Lapua headstamp but it was made for Lapua by someone else. Norma, I believe made it for them.
Weather or not it's worth it, really depends on if you think it's worth it. If you shoot alot, I would definately say yes. If you want the most durable brass money can buy, again, I would say yes. If you're looking to get the max out of your loads and want as many firings as possible, yes, IMO it's worth it.
Doesn't mean you can't make good consistent ammo out of non Lapua brass its just that, IMO, you will work harder and spend more time doing so.
For me, it's 100% worth it!