Not really sure what you are asking here but having done a few CC50s, one successfully (one boring and aborted for a good reason, and one an entire story in itself), I might be able to help a bit.
The usual southern route is Jax to San Diego or the other way around. The southern route is quite a bit shorter than the northern route and the basic difference is that you can get some sleep on the southern route. CC50's are strictly highway rides and honestly, a 'nicer route' does not really play into it- you will want the absolutely fastest route possible and that means all interstate highway.
The Iron Butt Association (those who sanction the ride) will not sanction this or any other ride they consider 'extreme' unless you have already done other IBA certified rides, at least one, and the minimum level ride they have is 1,000 miles in 24 hours, and it is called a SaddleSore 1000. And of course you have to have the previous ride(s) certified by them or they will not sanction a CC50.
I will say this though: if you can do it, it is one hell of an experience. The whole ride sort of melds in memory, at least they did for me, and it becomes something like watching a 48 hour movie that you cannot possibly remember so you end up with snippets that have no order or bearing on any other snippet.
Oh yeah, and if you plan on riding any decent distance (say, over 150 miles) after arriving at the CC50 destination, you will probably need a week or so to recover from the CC50 before returning. There is a deterioration in both body and mind during such a trip and a recovery period is needed, at least it was for me and the others I know who have done these types of endurance rides. My first one was 3,132 miles in 47:52 and I could walk at the end of it but I could not lift my leg over the bike- it left me pretty much exhausted and physically diminished and I while I could continue to ride (and did for another 80 miles or so the <other> way), I could not lift my leg over the bike's saddle.
Brian
The untimely passing of my brother this past November has caused me to re-examine my life's route, both past and present, and more importantly, future.
My presence has been requested, nay, demanded at the wedding of his youngest son in July of this year. Normally I would fly there on Friday and return to Phoenix on Sunday. "Can't miss a bunch of work" is my typical reply. NONSENSE! The world won't collapse if I take the time to ride there.
My thinking is ride the 1800 miles there, relax for a couple of days, then slide down to Florida and do a CC 50. The Northern Route is unappealing simply because I don't like cold weather. I would rather ride 500 miles in 100 degree weather than ride 200 miles in 50 degrees.
I understand that Jacksonville to San Diego is the shortest route but is there a "nicer" route using a different Southern city as a starting point? Perhaps Charleston?
School me up, please.