While Sarkhan has pretty lousy alternate abilities, Chandras +1 abilities let you pick off smaller creatures or dig towards extra action, both of which are useful at different points in the game
Costing six and not being able to immediately gain any life means you will have to do quite a lot of work just to get to stage you can make the Wurmcoil with any semblance of safety, if at all
Following on from past precedent, theres even the expectation these cards could be worth thousands of dollars each
My intuition has a strong track record so I've learned to trust it
These Artist Proofs, which include the Eyes, Path and Mushroom varieties of Forest, are easily recognizable by their blank backs and highly desirable to collectors
Remember that golden rule: Prototype is irrelevant if you arent casting the card and it's not on the battlefield