Although I rarely use this setup it does work well.
SignaLink USB for decoding. K1EL Winkeyer USB for sending. It sends cw via the cw jack on the rig. Not MCW.
I use DM780. The problem with software for decoding is this. It can not decode sloppy CW. Forget copying code sent with a bug! If it is well spaced and sent properly then the software will do a decent job of copying.
Keyboard code is perfect, as long as you spell words properly
Perfectly spaced and perfect letters. Easy to copy. Like listening to W1AW.