I was making the same decision recently, chose the Ruger GP100. A shooting buddy has a nice Smith 681, wanted one too, but all I found were well used and $$$. Considered a new Smith 686, but didn't want to deal with the internal lock, removal, plugging hole...
Opinions were that the Ruger was good, trigger not as nice, but easy to improve with a trigger job. So I went with the Ruger, did a trigger job on it, installed lighter trigger and hammer springs, very happy with end result. In direct comparison with buddy's 681 at the range, I preferred the Ruger's DA trigger. Link to thread for details:
Good luck with your decision OP.