Scrolling through Dunks and Threes (without a sub, you can see everyone but can't search), Lauri is a +3.7 (+4.6 Offense, -0.9 Defense), Sexton is a +2.2 (+3.8 Offense, -1.6 Defense). All estimates are wrong, but the three together point to Lauri being a slightly better player (1.5 extra points of value per 48 is quite a bit, worth about 4-5 wins in difference over the course of a season).
I was interested in a Sexton trade in concept earlier pre draft and FA, but I don't think that we're a great partner now. I think the Guard minutes are the strongest in terms of depth, and unless you moved to smallish lineups with Castle and Vassell playing a lot of SF, it's hard to make the minute distribution work.