For a beginner, I'd recommend going with something like the Luna Balls. The Luna Balls are available in two sizes -- mini, and regular. My understanding is that the regular set was intended more for women who have had children, but I've never had kids and the regulars a great size for me.
The Luna Balls are a little more expensive than the options you listed, but they're totally worth it. They give you multiple choices for the weight, so you can start out lighter, and then work your way up.
For a beginner, I definitely recommend getting a set that has a retrieval cord. The balls won't get lost in you, but from my own experience, it can be a real pain to get balls out without a string when your muscles aren't used to them.