I would get both. The artwork in Thieme's is the best I've ever seen in anatomy textbooks, but it's a relatively new source on the scene and they don't always provide the sort of angles/labeling/perspective for some hard-to-visualize or diminutive structures. This is true for every anatomy text, but Netter's comes pretty close and is highly refined through years of use and feedback.
Netter was very good at drawing things to illustrate a particular point. He didn't go for exact realism like Grant or Gray. So, if you are aiming for something that is a little more colorful with things illustrate in a way to highlight certain topics then go with Netter. I think the flashcards are pretty much equivalent since it has all the same plates as the book. I personally have Rohen's Color Atlas of Anatomy but real pictures can be a pain sometimes too when you are trying to understand the trend of structures and want to see where they lead better.
My class was one of the 'guinea pigs' for the Thieme Anatomy Atlases. The Thieme guy came to one of our last classes and asked for our input/feedback and gave us free junk (including a winking skull shirt). My PA school has our anatomy course at Harvard taught by one of their professors. The med school students used Netter but we used Thieme as our only atlas and Grey's for Students as our text.
It has a ton of useful boxes that summarize the material and the images are really nice looking. There is also an online component where you can quiz yourself by labeling images from the atlas. I actually only studied for practicals using the book and didn't put in any time in the cadaver lab (besides if I was dissecting/presenting) until reviewing for the final exam and got an A so...I think it's accurate and easy to use
it's the required anatomy text for our school (as of last year) and I thought it was pretty good. I grabbed a used Netter's prior to finding out I needed the Thieme- never used it. I particularly liked the online stuff at WinkingSkull.com- very helpful self-quizzing stuff on there.