it’s not entirely clear how you are connecting everything - as you seem to be using two different audio interfaces but the rule is:
Internal clock is ALWAYS better*
BUT…
If you are transferring data digitally then all the devices need to be synced to the same clock and there can only be ONE master clock. Either via an external wordclock or synced via the embedded clock in the MADI/ADAT lightpipe/AES/SPDif datastream (makes no difference which). Additionally the audio devices need to be told where to ‘listen’ to the clock (usually in the driver settings)
In your instance you need to work out which device is actually doing the A/D conversion and use that, as the conversion will have less jitter. Once audio is digitised and correctly clocked then the quality is ‘fixed’ and the DAW won’t care about INPUT jitter and the data will be reclocked when it’s converted back to analog.
I’m not clear which unit you are using as an output - but either way I’d rather get the highest quality recorded into the DAW and worry about the monitoring later. Again the D/A conversion is best when clocked internally but if you are using different devices for A/D and D/A then something has to give.
*(in 99.9999% percent of cases)