I have two bikes that get most of my saddle time these days..a flat bar Fuji road bike (with shortened bars and longish barends) and a Trek 520 w/ a long quill, short stem, and Nitto Randonneur bars. Each of these bikes will get about 1500+ miles this year. I like them both. I feel that I have just as many hand postions on the flat bar as on the road bars, though some would argue that point.

If the quill (or steerer tube) is equal height on each bike, and the stem is equal length and angle, you will still be stretched out further on the hoods than on the flat bar, because the road bars curve forward to the hoods. On your old bike measure the distance from the rear or front of your saddle to your flat bars, then compare it also to "the hoods" on your road bars. Measure the distance from floor to saddle and floor to bar on each bike. That may give you an answer to the relative position.

Remember also that tube angle and crank position play into the equation.