Part A is for hospitalization and Part B is for everything else, ie, doctor visits, labs, testing, etc. You must choose both of them when you are eligible or the premium will skyrocket later on if you decide you want it.
If you can afford it get part B. In what way do you have the VA? Is it for all of your medical needs and they will pay for any outside the VA care? That's how I would think about it. Consider what your future medical costs could be and then decide.
I use to work on Medicare appeals for Medicare receipients. The biggest issue they faced was not taking the part B and then regretting it.
You can send me a private message if that is best for you.
Take the part B Missy. VA doesn't have everything you need, such as issues for back pain. I recommend passing on the extra prescription drug coverage, as the VA covers everything, even if it is prescribed by an outside doc.