1. The older red slingbox pro unit does NOT have an HDMI connector. The connector was for the connection of an option "HD Connect Cable Adapter" which added an additional component video and audio connection and passthru output. this functionality is built in without the need for the additional expense on the slingbox pro hd unit.
2. Although the slingbox pro (the old red one) was able to stream an hd source with the addition of the hd connect cable; it was NOT an HD unit and could not steam in hd resolutions either in or out of network. The Slingbox PRO HD unit will steam in and out of network in HD resolutions if you have the vailable bandwidth to support that functionality.
3. the Slingbocx Pro HD unit will also function with aspect ratio changes as well as being compatible with the full resolution ipad app where as the slingbox pro is NOT.
4. Furthermore; the older red "slingbox pro" has been discontinued and the support is limited.