Hi Jerry,
Well, I`ve sailed neither ! Just looking at the specs you posted on both :

Personally I`d prefer the lighter boat (but you knew that already).
To justify 46% extra weight for 1ft extra length by adding sail area is where the design philosophies go in different directions, and you know which way I`d lean towards. However, the I-17R, due to it`s longer length should have more bouyant hulls, so it may be better suited to carrying it`s extra power, and could be better in waves (here extra length is an advantage, less tendency to "hobby-horse" althought Taipan is so well designed (By ex-Mozzie sailors ) that it probably does what the Mozzie does in waves, only better, which is to punch through, over or under them without a loss in speed. (No-one said it was a dry boat.)
Smaller boat should have lower sheet & control line loads, if you`re a 145lb weakling like me you`d go smaller, (although an article in an Auzzie mag stated that the Taipan`s downhaul control was a "hand-crunching" experience, similar to that of the Tornado, due to the wing mast they have.)

Just buy one of each, and see which one you prefer, then you can tell us all. I doubt you`d be unhappy with either.
Cheers
Steve.

Parting shot : If boats were women, you`d pick the one 100lb lighter, no matter what the additional cost !