As regards the odds, I think Crawford will be the favorite but the difference won't be that big. As regards who will possibly win, I think Crawford will.
Both men fought Porter and while Spence only won via split decision, Crawford won via TKO. In their match with Brook also, Spence knocked him out in the 11th while Crawford in the 4th. This is, of course, not a solid basis but I think, on the overall, Crawford has a much higher boxing IQ than Spence.
I agree with the boxing IQ, I would favor Crawford for that as it was evident in his previous fights. I mean he can adjust in the middle and then knock out his opponent. He can go to southpaw and orthodox and still be very effective.
So he might be a slight favor here, maybe 1.7 initially or higher and then Crawford 2.x but it will get closer as we near the fight of course as fans of Crawford might put big money that could sway the odds.