The X5365 operates at 3GHz, making it one of the fastest quad-core offerings on the market. It also will have a TDP of 120W, which is lower than other existing 3GHZ quad core units. The L5335 has less than half of that for TDP, though it runs only 33% slower:
With the energy-sipping Intel Xeon Processor L5335, Intel is delivering higher performance quad-core processors designed for servers that require optimal space and power utilization. The processor includes a 2.0 GHz clock speed and 1333MHz FSB within a 50 watt power envelope – or just 12.5 watts per processing core.
There's a huge price gap between the two units, with the low power L5335 coming in at $380 and the beefier X5365 flying all the way up to $1172 in bulk. You can read the full press release at Intel's site.