both rides are good stuff .. i rode them both in 2002, the first year i started riding and getting serious about training. i fell into riding with a group of racing guys last summer, and they have convinced me to train and race this season. but i might be convinced to do STP in one day this year, we'll see.
some of the guys i did STP with in 2 days, had done it in1 day the year before. they all agreed that they had more fun doing it in two days. just a thought for you. either way, it's a relatively flat ride, last 1/3 is more rolling. lots of good people and good food and lots of fun, either way!
as for the chilly hilly, they're not kidding about the hilly part! i have to train on that gargabe ... but you've gotta train your weakness! 
happy training!
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Things should be made as simple as possible, but not any simpler.
-- Albert Einstein (1879-1955)