I'd go with affection, too. The 7k necklace might be of comparable value but not the others.

...Long term you'll get both - the question is, what sources are their of 2nd affection items? If we'll see more of them then, probably the necklace is best in the long term

Bear in mind as well that the necklaces will be available for each set of whaleship missions, while the other items may not (the last round of Mission 2 maps, for instance, only had the necklaces in the shop). Stock up on the consumables as needed first. Later mission maps will award more medals which makes the necklaces easier to obtain so don't stress it too much now.

Oh, and those second affection gifts will take you to 90%, not 60%.

When will we be able to exchange 3* and above for 2nd affection items currency?