From Dallas to CS there isn't 10 minutes difference in 45-14-6, 45-OSR-21, 45-21 or 35-6.
45-14-6 is the shortest distance wise by about 10 miles, but because of slowing down through the small towns it turns out about the same time. You better slow down because you will get a ticket.
45-OSR-21 - I don't like it at night and for a while OSR was about as bad a road as you could drive. Most of it is repaired now, but truck traffic is still problematic.
45-21 - is probably the easiest drive other than the 2 lane section of 21
35-6 - might be a couple minutes longer, but since 6 is 4 lanes now and 35 is mostly finished, it is an option.
I've done it from Frisco for almost 30 years now and will almost always take 45-14-6, but occasionally 45-OSR-21 during the day.
I've timed them all and done mileage and it really just comes down to personal preference.