Hi Cl:
I own and wear all 3 models (and also have a small wrist). Comparing the 3970 and 5970 is like comparing "apples and oranges". Even in the same color they are markedly different watches, both aesthetically and size wise. The 3970 for me wears "much smaller" than the 5970. The fact that one is rose and one is white accentuates the different look (see Zane's beautiful photo). For me, of the 4 metals, the 3970 looks best in rose. The 5050 is by far the nicest looking recent perpetual and pretty rare; however, yellow is by far the most common 5050. If you prefer the 3970R to the 5050J, I wouldn't let the fact that the 3970 and 5970 share the same movement deter you from buying the 3970. No matter what you do, you win, which is a very nice position to be in. Please let us know what you decide.
Best,
David