Category 5e:

• CAT 5e approved in January 2001
• The primary benefit of CAT 5e is improved operating margin for 1000Base-T (Gbe) signals
• Most currently accepted installed cable for LAN infrastructure
• Typically only to 100 MHz of bandwidth
• Premium cables were available to 350 Mhz

Category 6:

• CAT 6 approved in June of 2002
• Published as TIA/EIA-568-B.2-1
• Higher bandwidth headroom of 250Mhz per pair
• Category 6 cable is required for TIA/EIA-854 full duplex 1000Base-TX Ethernet specification
• 1000Base-TX less expensive than 1000Base-T