What is the advantage versus large primers?  I presume it may help in keeping the pockets from loosening over multiple loadings but I'd like an official answer.  Is there any real benefit as far as accuracy is concerned?  Asking because I just picked up 200 rounds on clearance at Academy of the Hornady Black 140 BTHP which uses large primers.  I was planning on reloading the brass for my Bergara HMR once I had it well broken in.  Now I'm wondering if I shouldn't just bite the bullet and go Lapua...

David Tubb and a grip of others have noted that small primers in these 35-45gr capacity cases make exactly the difference I have seen from them myself, dick all. I, and many others, are of the opinion that small primers are starting to be on the inadequate side with powder charges much over 35 grains. The small primer pockets are better at not stretching out from loading hot because there's more brass to resist it. Don't load so hot that your primer pockets stretch and it's a 100% moot point. I have match brass that has 20+ loadings on it and the primer pockets are still tight as a nun's snatch. That ammo doesn't get loaded hot, there's no reason to on those loads for that specific game. I have other match loads for entirely different games that make brand new brass into one-hitter-quitters and will usually pierce primers on every shot. That is done knowing it's bad news but it's the only way to be competitive with that rifle (a .223) and once fired .223 brass is essentially free.

SRP creedmore is a fad.

The consensus when 308 Palma brass came out was that it could handle up to 45 grains of powder with a SRP.  And, there are plenty of palma, across the course, and FTR shooters swearing by it.
Contact Kevin Thomas at Capstone Precision group to get some more thoughts!  
Somethings are fad....like when 6.8 SPC came out....Rem brass was LR vs the rest being SR.

I'd say case life.

The flip side of that is they hide pressure more than a large primer does, and that's not a good thing.

I run SP in all my short action cases currently.

The advantage of SRP brass comes with case life; the pockets won't loosen on you as fast.

That said, it can have downsides in certain conditions. Namely in colder weather, with large powder charges, they are more prone to hang-fires than LRP.

Case life.

That said, I lose about 30% of my hornady brass after 10 firings.  Most of those are due to warm loads under a 142smk.  It's always the primer pocket that goes.

I think 12-14 reloads out of 6.5 LRP Hornady brass is absolutely doable provided you don't hotrod them too much.

I've got a box of Lapua brass that's sat unopened for 2 months. Just don't need to use them.

Bolded part has been 100% my experience.

My experience is that if you keep Hornady cases under 65ksi you can easily get well over 10 loadings from them.

Primer pockets letting go is a good sign that you're going over 60-65ksi.  Lapua cases can maybe handle it and keep chuggin', most others can't/won't.  I guess speed is nice, but I prefer to use the same 200 cases for the life of my barrel.

Case head separation or excessive stretching would also indicate that.  I've had some Hornady pockets go after 5 loadings and nothing too warm.  Considering the cost, it doesn't bother me too much.

Now my 142SMK load?  No doubt about it, it's warm. 42.9gr RL16 with a COAL of 2.81.  I made 20 rounds and still have 5 left, I think I'm going to pull those down.  2950fps with an SD of 7.