I haven't used the Andrea stuff so no idea what that's like but I can highly recommend MagicSculp, I think it's one of the best putties available and it's especially easy for new users to get along with - it blends really easily and leaves nearly no residue on the fingers if you're mixing without gloves, it's not overly sticky, has some lovely working characteristics and a long working time (up to 3 or 4 hours if it's cold).
Since you already have them, it's worth trying a blend of Milliput and Kneadatite (greenstuff) which makes quite a nice sculpting material, in many ways better than either one by itself; MagicSculp and one or two of the other epoxy sculpting compounds are somewhat like this blend, without the hassle of mixing twice and then blending.
Lots of previous threads on sculpting if you need tips on working method or tools.
Einion