As a disclaimer, I am going to digress some from your question.
I would say that this really depends on how much and what type of equipment you will be placing in this IT Center. If you will be primarily placing equipment requiring backup power other than servers in this space (i.e. voice switch/ksu/pbx, ethernet switches, CSU/DSUs, Routers, and the like), I would say follow the lead of the telecom industry and use a -48volt distribution system within the room. This type of setup has a higher initial cost, but is beneficial from a reliability standpoint. First, most equipment of this nature comes with the option of a -48v dc power supply (which tends to produce less heat than it's AC counterparts). Second, you can centralize your battery backup in a single location instead of having to place them at the equipment. Third, most of the equipment of this type will have optional secondary power supplies, which can be supplied by different fuses/CBs off of the same or a separate -48v dc power bus. Then you could change out a power supply without having to power down the equipment (just the PS that you are going to replace). Lastly you benefit from the decreased potential for harmonics on your signal wires from AC lines being in close proximity to signal wires. As for powering the rectifiers, I would say 3ph 4-wire WYE, and because the rectifiers are balanced you should not have to up-size the neutal. You would then have a secondary power connection (this time as 120v AC) going to those cabinets that are housing servers and other equipment that do not have a -48v DC power supply option.
If instead you are primarily providing power to servers then I would suggest the 3ph 4-wire WYE configuration, but this time you will likely have to up-size your neutral conductor as most IT equipment operates on 1ph 120v (which means it would connect from 1ph of the 3ph system to neutral).
PS the -48v dc system is normally only feasible in larger systems due to the higher initial cost for the power distribution system.
From the strictly AC standpoint, I would still say 3ph 4-wire WYE especillay considering most modern IT equipment uses a switching power supply and is less suceptible to problems with the incoming power and thus should not require neutral be separate from the bonding conductor (except from the distribution panel to the 1ph equipment).