Peterson vs lapua ?

Lapua is always my first choice if it is available in the headstamped cartridge I am looking for.
Peterson is very good as well. Probably a close second.
ADG a close third, but ADG needs to refine their "ready to load" status. I have not had a single piece of virgin ADG brass that did not need chamfered/deburred right out of the box. Also, ADG is the ONLY high end brass that I have found QA let damaged brass slip by. Granted, I have loaded THOUSANDS of pieces of ADG brass, but have found a total of 5 pieces that are totally unusable due to case deformities. One neck with a big chunk missing and some weird piece of trash brass stuck in the neck, and 4 with forming issue/damage on the shoulder. ADG CS was always great and shipped out a few replacement pieces no questions asked though.
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This looks like typical bags of Winchester brass I've seen.
 
I load primarily for a .338 Lapua Magnum. The Lapua brass works just fine. But the Peterson brass is dimensioned a tad too wide between the rim and the case body. My one tool that has an expandable case holder works just fine (with a bit of pushing) but the Peterson brass won't fit the RCBS case holder. Not an impossible problem, just an annoyance.
 
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