i'm gonna try to answer as many of your questions in as succinct a manner possible. here goes:
"I was wondering what the difference was really?"
no real difference, per se. but if you're using the 4k for sequencing and recording your midi keyboard into the 4k i would allow the mpc to act as master. ableton does a bang-up job of following along dutifully and this allows one to use the mpc's transport controls to control everything.
"I know using "Midi Clock" and "Receive MMC" set lets you run anything off your 4k thats recorded in a sequence by pressing the play button in Ableton. Also using "Midi Time Code" and setting "Send MMC" under the sync out option lets you run Ableton when pressing the "Play Start" on the 4k. What is better to use?"
all ableton needs is midi clock, no need for MMC (midi machine control) or MTC (midi time code). in my experience, most hardware can follow midi clock. my eventide processor and virus synth both keep up this way. now, as to which is better - this is up to you.
"Also i'v seen people hit "REC" on the 4k and start playing something like a bass line or ect, on a midi keyboard and are able to record it right into that sequence onto a track. Or is it overdubbing only? Either way anyone know what needs to be set in order for me to record from my Keystation 88es over a sequence on the 4k? I was also trying to record a sequence from my 4k into Ableton but its not recording anything. Any thoughts? Thanks."
REC records and OVERDUB overdubs whatever is showing up at the midi ports into the current track. for example, you have your keyboard plugged into MIDI I on mpc and you hit REC + PLAY the mpc counts you in (provided you have this enabled) and then records whatever data shows up at the midi port. pick a midi out connected to a sound generating device (although you've invariably already done this so you could actually hear what you're playing) and it should play back what you've recorded.
i STRONGLY suggest you spend some quality time with the manuals for BOTH the mpc and ableton.
