I think the processor is slightly faster. The specs are here:
▪Open-source Linux operation system
▪Full compatible with Enigma2
▪Broadcom 750 MHz Mips processor
▪Fixed 1 x DVB-S2 Tuner
▪Optional detachable Tuner (DVB-S2 / TWIN DVB-C / DVB-C/T2)
▪256 MB NAND Flash / 512MB DDR3 RAM
▪Media Player
▪Downloadable Plug-ins supported
▪MPEG2 / H.264 Hardware decoding (DVB Compliant)
▪Unlimited Channel Memory
▪Super sensitive tuner for very weak signals and weak transponders
▪1 x smartcard reader
▪10/100 Mbps Ethernet interface
▪2 x USB2.0 PVR Ready ports via a USB external device
▪1 x HDMI Interface
▪A/V out
▪External IR Sensor
▪1 x internal SATA connection for 2.5" HDD
▪Fast channel change
▪Extended EPG and recording reservation on EPG
▪Various Plugins
▪Bouquet lists
▪Multi language OSD, Skins
▪Fully automatic, Manual Channel Search
▪Timer & multi-event recording
▪Teletext & Subtitle support by OSD and VBI
▪DiSEqC 1.0, 1,1 ,1.2 and 1.3(USALS) compatible
▪under 0.5 Watt Stand-by power consumption option
I've got a Mutant HD51 on pre-order, should be here at the end of the week.