The reality is a lot of the coaches who have been talked about are good candidates for different reasons, which makes sense because right now we're pretty much in pure speculation territory and people aren't likely to put forth a candidate that doesn't have at least a strength to make the hire look appealing to those who prioritize certain things. There also is not a perfect hire and we aren't likely to go after, or afford, the absolute best hires so those names aren't being put forth. So everyone comes with a downside that will likewise cause some people to not want them.
Obrien, Chadwell, Sanders would all almost certainly be seen as good hires by most of the football world.
Obrien fills in a lot of the boxes for those that like P5 experience, ties to very successful programs, and personal ties to GT. But he lacks the innovativeness some want, and his head coaching experience, at the college level, is limited. Basically he's a typical power team coordinator that has been getting looked at recently by a lot of places. We wouldn't be hiring him for his xs and os, but rather his ability to run a program.
Chadwell is the classical supper successful at a lower level coach and also appeals to those who like innovative offense that doesn't come with the stigma that was true with Johnson's offense. He also has questions regarding whether he could recruit well enough and whether the staff he'd put together would be as good as we need here.
Sanders is unique. There really isn't a good football equivalent to compare him to. He's a legend both in the black community but also in Atlanta which is an intersection that makes him have the highest recruiting potential we could hire, but has little in the way of coaching experience to lean on. I'd say the closest comparison I'd make is Juwan Howard at Michigan. Basketball has had a couple of closer comparisons, Manning at Wake, and Stackhouse at Vandy, but its relatively new territory for football unless I'm missing someone.
Same for the others that have been talked about but those three seem the most three discussed.
None of the three would be a bad hire in the moment. Any of the 3 could end up being a bad hire in retrospect. Personally, I'd rank it O'Brien, Chadwell, Sanders because I think having experience at the P5 level is important, and O'Brien is also the most likely to put together a higher quality staff. To me, with Chadwell I ask the question of other than offense what are you bringing to the table with him, and if it's primarily his system, why wouldn't we go after one of his OC's instead to be our OC instead. Otherwise I think he is more likely to just bring his staff mostly intact which I'm not sold on being great. Sanders is interesting, and I wouldn't hate the hire, but it's such an experiment that I'd rather pass on at the moment.