Hi all, While this is my first post, I would like to state that I've been lurking here for a few weeks and have run dozens of searches. The info, experience and advice here seems top notch.
Still, I have a few things to run by the over 50 crowd in particular. Please bear with (or just ignore) me as you see fit.

First about me/situation: I'm 51, 5'7", 220 ( yea I know :-() and not particularly athletic although I do walk a little daily. I'm now trying to get into biking again for exercise and fun. I've got a few friends that bike ( one road bike, one flat bar) but I'm not sure how much I would ride with them. Basically I plan to do mostly 5-10 mi back road trips with the occasional ( 1xmonth?) 20-25 miler. I don't ever see myself going much longer than that as my time is limited and hobby interests broad. Roads/paths around here (MASS/RI) are paved but spotted with pot holes, bumps, cracks etc. My last bike was bought in 97' and is a 33#, 1.9" x26" tired Schwinn hybrid with full upright position and shock absorbing seat post, etc.) Super comfy, and it did all these things OK, but I think I'm ready to give up A LITTLE comfort for some speed/ bike lightness to help concur hills and motivation ;-).

So given my gut, age and general "needs", I've been thinking that a flat bar fitness/road bike would do the trick. Then I start reading about hand fatigue and ( 5-10 min) test riding and wonder if I would be better served in the long run with a road bike ( like a Fuji Newest, Cannondale Symapse.) My dilemma is this: I THINK the flat bar ( like a trek 7.3/7.5 , Fuji Absolute 2, Jamis Alegra 2) would suit my needs best but worry about outgrowing it quickly. The road bikes ( like the Fuji Newest I tried) were lighter and faster but I worry about the effects on my back and potential flats on local conditions. (p.s Only road bikes I would consider would ahve to have the extra brake levers on the top hold position as well.)
I have a decent budget of $600-$1000 or so but unfortunate in that the 8 LBS's I've visited are low on stock in my (small/15") frame size.

Couple of specific questions:

Will I really reap teh benifits of a $1000 frame/component set over a $600 set?
Will the road bike positioning be harder to get used to. ( If she sits int eh garage because i don't Love it", it was wasted $.
Will a 24# road bike ride that much fastr/easier than a 27# flat bar set up?

Constructive thoughts and advice , both general or specific are welcome!

Thanks in Advance,
Dave