If you look at all the time that both Smart and White have been on the Celtics (a little over a year), Smart has been better for all of that time except for the last 10 or 15 games or so. And Smart was better against CLE last night.
No doubt that White has played some of his best ball the last month or so in contract to Smart coming back from injury and playing poorly (until last night where he looked like the old version of Marcus). So sure, if you compare best of his career stretch White to coming off injury Smart, you could conclude that White is better.
But to me, if you look at it in its entirety, Smart has been better overall, and at times, significantly better. At this point, I still ride Smart over White but they are close. What a luxury to have both.