Which of my components has the better built in DAC?

I am willing to bet that McIntosh does a better job of implementing whatever DAC chip is used.  It isn’t just the chip, it’s power supply, the isolation, the quality of the associated parts, etc.

  My Oppo 105 and first generation Mytek Manhatten DAC had the same chip and the Mytek was far and away the better DAC.  The Mytek cost 8 times more than the Oppo, and the Oppo also had video and networking responsibilities.  It was and is a hell of a machine, by the Manhatten was optimized to do just one thing, had a lot more boom boom in the power supply and everything else.  To me it was a fantastic demonstration that the chip alone doth not a DAC make.

  Without checking I am guessing that the Mac costs more than the Bluesound and I am cert has more of everything needed to optimize chip performance 

I am guessing the Mac has a better DAC, but it does come down to listening. As for the connection, ignore optical, it is down to USB or Coax. Using coax, all of the clocking ( and jitter) will come from the source, I.e. the Node. With USB only the data will be transferred and the clocking will be handled by the DAC. If we give the overall nod to the Mac, go with USB. And cables do matter, watch the used market and get something decent, lots of recommendations can be found on this site.

You have the gear, run the experiment. The NODE DAC isn't broken, but it can easily be bested by a standalone DAC. Easily doesn't mean veils lifting and wives noticing.. Improvements will likely be nuanced and subtle, but crucial, in my opinion.

With my standalone R2R, USB from the Node gives the cleanest and smoothest sound. Again, you will have to try. Implementation often dictates topological advantages*. (See: XLR vs RCA)

You have few ways to connect there -

1. RCA out from Node into Mc

2. Coax out from Node to Mc

3. USB out from Node to Mc

4. Toslink out from Node to Mc

Try it all. My suspicion is the Node into C2700 via USB will sound the best with second best option being coax into C2700. I don’t think the DAC in the Node with node’s analog outputs into mcintosh will match the digital connection.
But it’s worth exploring it all. You never know what will sound best to you. 

Your Mac's DAC should sound better to you.  I would try both coax and USB for the connection.  The biggest difference will be using the USB connection clocking will be done by the Mac which may sound better.