Re: POF .308 + Suppressor question...
I've been running my AR's suppressed (80% of the time) for about 6-7 years now, 3 of which has been on piston uppers. Suppressed piston uppers still get dirty but it is only half (if that) of the DI gun and on top of that the residue is isolated to the mag well, bolt (front half'ish) and a bit around the chamber opening inside the receiver. This is with with cleaning every few hundred rounds if you must.
I once wanted to see how many suppressed rounds I would go before a failure and ended up cleaning at about 1,500 rounds due to a 4 day class that coming weekend. Didn't need to and I actually wish I hadn't but it is what it is.
The cleaning of the weapon is also WAY less labor intensive over the DI as the piston guns generally don't burn the residue on so you usually wipe most off with a (solvent) dampened rag then very little effort to get the remaining.
I had the POF, Bushy, and LWRC and sold all except the LWRC. Look at all the systems and each companies CS and I'd be suprized if you went any route but LWRC.
No, I don't work for or with them in any way other than being a satisfied customer on multiple occasions.
Hope that helps a bit.