That comes down to what you like and are willing to tolerate! We often have traveled that route and have definite thoughts on what WE like. We avoid the "kill zones" along I35, if at all possible! Austin to Dallas is not on our list if there is another way.
If absolutely sure you want to go to Durant, that kills part of what we would do as we would drop South on I45 to Fort Smith, Ar. for a much safer trip and nicer territory, then we admit it is a bummer from there South but we have no safety concerns along that route.
Totally much safer and far more fun as it has trees and quiet versus traffic that gets up every day regretting being alive!
We avoid Dallas when we can and if we must, we avoid the route through from 75 to I 35, due to bad lane changes at that spot in South Dallas.
We do come/go that way if we are going in Eastern OK, though.
We find the point to come off 75 to I45 is an easy one as it seems to just morph, rather than a total change! I45 on South ,we feel much better than 35!
But , if you MUST?
We feel there are points to avoid in the change from 75 to get to 35!
If we have to, we go down to the intersection with 20 and then jog back West to 35! Slightly more miles (3-5?) but far less crazy!
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The East Ok or West AR are not good for speed but we tend to drag more than speed anyway! Nicer country and nicer drivers! For campsite we tend to go for trees and country over the hustle!
Current note for construction as it is everywhere? I35 through the Austin area is prone to being bad for the next 5 years as they are beginning work to do "something" through downtown. There is a bypass on toll 130 but it is mot worth the trek for most folks so they are starting with more lanes through town but have not got the final plans, so it is just beginning on rebuilding the bridges, etc. and that means lanes closed!
We are on the East and North so no need to go into that most of the time!
Currently the work is night work but the lanes are still closed at different points!