I'd take Spence but this fight won't be anywhere near close to happening anytime soon.
They'd both have to remain undefeated and both have top resumes for the public to demand this and it would still take a while considering the circumstances around Crawford's promoter's reluctance to work with Haymon.
As of right now, I think Crawford has more experience. And because Crawford can switch up styles, plus switch stances, he could make better adjustments and win by points. By no means would it be easy. But in about 3 years, Spence will be the most dominant p4p force in the sport.