kind of hard to compare on prices, as there's a lot of variability on parts prices. you could have two very similiar looking uppers, and the price could be quite a bit different due to parts used (chrome lined barrel vs not, higher end hand guards, etc).
PSA's prices though seem to be right in the same ball-park as Del-Ton. A lot will come down to what you want as well. AR's are like legos, and you can build one just about any way you want.
This sums it up well. In my case I wanted a dissipator with a heavy barrel so my only option was Del-Ton. Someone else might not want the extra weight of the heavy barreled DT so they go with the lighter PSA, while another person might say that they prefer the 1 in 7 twist versus the 1 in 9 twist or vice versa because of whatever bullet weight they want to shoot. Another guy might not like the full length gas system of the DT as opposed to the midlegnth gas system of the PSA. Lots of internet experts told me my rifle should be a jammo mattic because of that and it still runs. Another person might just look at the two and buy whatever is cheaper or on sale that day too so who knows. Basically there's enough options out there in the AR world that we as gun owners & AR builders/assemblers get to be some pretty picky eaters.