I'm just finishing up my sbr build. It's a 10.5. The upper is complete PSA. The lower is all Spikes with a Magpul MOE stock. My question is the H buffer the best way to go? Thanks.

I run an H3 in my 11.5", both suppressed and not.

I'd say H2 or H3

i use an h2.
h3 was nice but i run with and without suppressor and wanted the reliability.

Same here. Seems to work great with the h2.

H2 for starters.

H3 in a semiauto if your setup will lock back on an empty mag with your desired ammo. Shooting cheap range ammo unsuppressed in a properly ported 10.5” might require an H2 or H1.

I run an H3 in my Colt 10.3” suppressed and H2 unsuppressed. The H1 cyclic rate is crazy fast. The H3 cyclic rate unsuppressed is a bit sluggish for my tastes. My lunchbox sized range toolkit usually has minimalistic cleaning Kit, takedown tools, lube, and spare buffer.(CAR/H1/H2/H3/XH).

Life hack: buy an H3 and a CAR buffer. You can disassemble the buffers and mix/match the steel & tungsten weights to make a CAR, H1, H2, or H3 buffer as needed.

H2 would be my start no question

ON my 10.5" PSA upper i am running a H2 with a heavy spring.  Runs perfect in my rifle with this combo.

I also have an 8.5" upper that i run an H3 with std spring but an adjustable gas block to fine tune it where i wanted it.

To better answer the OP, some more information is required.

What is the gas port size? Sometimes PSA will tell you over the phone, sometimes they won't. They definitely don't list them.

What buffer spring are you using?

What ammo are you using?

Will it be ran suppressed?

I run an FN H6 in my 7.5" SBR just because I had it lying around. Use H2's and H3's in others. I can't tell the difference, they all work.