Cat6 cables, also called Category 6 or Cat 6 cables, provide lower crosstalk, a higher signal-to-noise ratio, and are suitable for 10GBASE-T (10-Gigabit Ethernet), while Cat5e cables support only up to 1000BASE-T (Gigabit Ethernet). As a means of future-proofing your network, Cat6 is generally a better choice and worth the small premium in price. Cat5e and Cat6 cables are both backwards compatible, which means newer Cat6 cables can be used with older Cat5e, Cat5 and even Cat3 equipment.
Both Cat5e and Cat6 are twisted pair cables that use copper wires, typically 4 twisted pairs in each cable. The specification for Cat6 features more stringent specifications for crosstalk and system noise, and provides performance of up to 250 MHz. Cat5e, in contrast, performs up to 100 MHz. This was often achieved using a spline (a longitudinal separator) in the wiring, which isolates each of the four pairs of twisted wire. However, this made Cat6 cables more rigid; newer cables use other methods to reduce noise and are more flexible. Regardless of whether a spline is used, a cable that meets Cat6 specifications provides significantly lower interference or near end crosstalk (NEXT) in the transmission. It also improves equal level far end crosstalk (ELFEXT), return loss and insertion loss compared with Cat5e. The result is less noise, fewer errors and higher data rates in the transmission of the signal.
edit How to identify
The category is almost always printed on ethernet cables. It is not possible to identify cable categories by color, but Cat6 cables are often thicker than Cat5e because it uses thicker copper wires.
edit Maximum Length
Both Cat5e and Cat6 cable specifications allow lengths up to 100 meters, but Cat6e has a lower max length (55 meters) when used for 10GBASE-T (10 Gigabit Ethernet). In order to run 10GBASE-T for 100 meters, Category 6a cable, or Augmented Category 6, cables need to be used. Cat6a cables allow performance up to 500 MHz.
As mentioned previously, Cat6 cables can be used to power 10GBASE-T, or 10 Gigabit Ethernet, while the maximum that Cat5e cables can support is 1GBASE-T, or 1 Gigabit Ethernet. This is because Cat6 cables perform up to 250 MHz, more than twice that of Cat5e cables (100 MHz).
The price of ethernet cables vary by length, manufacturer and seller. In general, Cat6 cables are 10-20% more expensive compared with Cat5e cables. However, cables are generally cheap and the speed boost offered by Cat6 cables usually makes the price premium well worth it, even for home use.