Delta is really good, probably better than HiPro, another good brand often found in Dells. The only drawback may be the Chinese Ltec (Luminous Town) capacitors found in most Deltas, but Ltecs seem to hold up OK in PSUs, unlike the case with motherboards.
Here's my old 300W Delta, made in 1999 with Japanese capacitors. A year ago I sampled about 6 of the capacitors, and they all measured good for capacitance and ESR. The filter chokes on the outputs are bigger than normal for 300W PSUs, as is the transformer, despite the fact it runs at 100KHz, or almost twice the usual frequency for that vintage. Generally the higher the frequency of a transformer, the smaller it can be for any given power capacity. The big vertical board on the right handles overvoltage and controls the fan (fan speeds up not just with temperature but also with load), while a much smaller board under the big heatsink on the left controls the voltage regulation and uses a chip custom made for Delta. I was able to get 450W out of this 300W unit, at least for about 10 minutes (my load resistors got too hot after that).
Here's a review of a newer 650W Delta: