Both have similar specifications when compared to the PPK/S. The Sig's dimensions are larger, but it is also lighter, especially in the aluminum versions.
If it were up to me, I'd get a PPK/S, but this is just because I like the look of the PPK/S more than that of the Sig. I haven't handled a P232, but the PPK/S fits my smaller hands perfectly.
When you look at the responses you get, keep in mind that this is a Walther forum - you'll probably get some more Walther-positive votes here.
Post the same question at a broader forum (Gun Review Forum or the like) to see what other people think.