Some of this is also going to depend on your spending. I like the Earth cards because they have a very low annual fee compared to most other reward cards and since my spend isn't huge, that's quite important to me. Every dollar spent on fees is basically eating into the value of your rewards points.
At the moment I think Earth+ is probably the cheapest annual fee for a card with travel insurance (since Citibank's Fee Free Gold seems to have gone) so if that's important to you then it's good value too.
On the aesthetics side, well, it's really a matter of personal preference, but again, the simple, clean, understated design of the Earth cards appeals to me, though I wouldn't really pick a card based on the design anyway.
