I75 North from Florance KY thru Cincy

If I'm reading your post correctly and you're going to be heading south on I-75, taking I-275 wouldn't buy you anything as the lane restrictions on I-75 are south of where I-275 reconnects after bypassing the city. Bottom line is that if you are wanting to head south into Kentucky/Tennessee on I-75, there isn't a good way to bypass the area of construction around Florence. Personally, if towing, I prefer I-275 to avoid the Cincinnati traffic and especially the I-75 bridge over the Ohio. But that's me...

It will take you about 20 minutes long IF THERE IS NO HOLDUP on either road. If there is stopped traffic, who knows? Check Google maps about 15 miles north of Cincy and see if it is showing red (stopped traffic) or yellow (slow traffic). If it's all green, just head on down I-75. If it's yellow or red, head around I-275.