So the sig basses all have ever so slightly different pick up places from the normal models even though they apparently look the same.
The Grand Dark has a longer scale length and the a dark Glass tone capsule, with Sandberg black label pick ups.
Ida will be more like the type of music she plays but still versatile, the Grand dark is punchy, goes deep and has the 3 band EQ Bass, low mid, high mid.
They both feel great and although I am sitting on the fence a little as it will depend on what you like, what else you play through pedals/amp etc. You will get a quality bass either way