So I am, for the first time, building an AR-15, and I am a little confused.

I've decided to use a "fixed position" fake telestock. But I've noticed two different kinds out there. The first (cheaper) version seems to use a shorter "carbine" buffer, while others, namely bushmaster, uses a "full-length A2" buffer and tube. I think I've figured out the obvious: collapsing (real) telestocks have a shorter buffer, tube, and possibly spring. So my question is, which is better? My guess is the full-length, no doubt, but is it "twice the cost" better? I can't seem to find the longer variety for under $99. does this even matter? most retailers don't even bother to tell me what variety the stock is.

is it possible to build the full-length variety cheaper?