The biggest thing that makes the server power supplies so much better is the price per watt ratio.
I've got a 24V 1150W power supply made out of two HP DPS600PB server supplies. The power supplies were £5 (8$) each (used in a server but like new). Nearest equivalent hobby unit is the Junsi S1200.. that comes in at about $300.
The server power supplies are also designed to load share so if you want more power you can very easily make a quad unit with 2300W capacity! You can also get power supplies with greater output than my DPS600PB. Modification of the DPS600PB is very easy, personally I wouldn't pay more than a few bucks extra to buy one pre-modified.