There are going to be a bunch of things to consider. Is Marcus 100% or is he on a minutes restriction at first? How does this affect the match-ups?
Everything else equal, I think you go back to what worked best over the course of the season, Smart in the starting lineup. But there might be other factors.
But I don't think what we did this season worked all that well. In 2017-18, Brown started throughout the season and we ended up with a considerably better record...and that was with Irving going down.
I understand that after the first 20 games this season, Brad needed to make a change, but I think with everyone finally settling into their roles (it only took like 75 games), Morris and Smart off the bench works better...that is just my opinion, though