Help me choose: OptiPlex form factor

OptiPlex desktops are available in multiple form factors because businesses have different deployment needs. Some form factors allow for greater system expandability. Others enable deploying systems in space-constrained environments or in environments where it is desirable to have the system installed out of public view.

Chassis for the OptiPlex form factor options can feature:
  • Toolless internal access to the system and components allows for quick, easy upgrades and service
  • 10 percent postconsumed recycled plastic in chassis
  • DirectDetect™ front-panel diagnostic and network LEDs display status of hard drive activity and network connectivity quickly and conveniently
  • Minimum of two USB 2.0 ports located on the front of the system for easy connectivity to USB peripherals
  • Built-in hand grips on mini tower and desktop chassis

The system you are configuring may or may not include all of the options listed here.

If your primary business need for this system requires ... Choose ... 
Greatest number of expansion slots and media drive bays, where deployment space is not an issueMini Tower
Expansion slots and media drive bays that allow for a high level of expandability where desktop space is adequateDesktop
Fewer expansion slots than either the mini tower or the desktop form factor, in a size that allows for deployment in smaller spaces and support for AIO stand Small Form Factor
No expansion slots and fewer media drive bays than the mini tower, desktop or small form factor, in a size that can be deployed in the greatest number in almost any place, including out of sight and support for AIO standUltrasmall Form Factor 

 Mini Tower  DesktopSmall Form Factor  Ultra Small Form Factor
Systems Offered  Mini TowerDesktopSmall Form FactorUltrasmall Form Factor
Dimensions (HxWxD) Inches/(cm)14.2 x 6.9 x 16.4 / (36.0 x 17.5 x 41.7)14.2 x 4.0 x 16.1 / (36.0 x 10.2 x 41.0)11.4 x 3.7 x 12.3 / (29.0 x 9.3 x 31.2)9.3x2.6x9.4/(23.7x6.5x24.0)
Minimum Weight (lbs/kg)19.55/8.8716.67/7.56 12.57/5.707.20 / 3.27
Number of Bays2 internal 3.5"
2 external 5.25"
1 internal 3.5"
1 external 5.25"
1 internal 3.5"
1 external 5.25" (slimline)
1 internal 2.5" 1 external 5.25" (slimline)
Expansion Slots1 full-height PCIe x16
1 full-height PCIe x16 (wired x 4)
1 full-height PCIe x1
1 full-height PCI
1 half-height PCIe x16
1 half-height PCIe x16 (wired x 4)
1 half-height PCIe x1
1 half-height PCI
1 half-height PCIe x16
1 half-height PCIe x16 (wired x 4)
1 mini PCIe connector
Power SupplyStandard 265W PSU or optional 265W up to 90 percent efficient PSU.Standard 250W PSU or optional 250W up to 90 percent efficient PSU.Standard 240W PSU or optional 240W up to 90 percent efficient PSU.Standard 265W PSU up to 90 percent efficient