I've got an 06 RKClassic (for sale) and a 08 Ultra. Both are sweet rides.
I had the same problem deciding when I bought the 08 (RKC, SG, or Ultra).
I'm glad I went with the Ultra.

 

i prefer the looks of the RKC to any stock SG. the rkc is much more versatile than the sg too.... shield, no shield- fairing, no fairing. both added (or removed) changes the look tremendously.

i also REALLY like the rear of the RKC- the bags look tapered whereas the sg (and all hard bags) look more like boxes which were an afterthought.

but- if i had to buy a new HD- im not sure what id get.

 

I bought the Road King and one week later traded it in for the Street Glide. No regrets looking back. The SG fits me so much better and even though there probably close in weight, the SG feels so much lighter.