Whats the difference in these lenses?

I have the Sony Alpha A200K DSLR camera and it came with a 18-70mm kit lens. I want a macro lens to get really good clear close up shots but its 50mm. isnt my 70mm better?

Well, no. Having a longer focal length or more zoom certainly does not make a lens better. In fact, zoom degrades the quality of images produced by lenses. The best lenses (quality-wise) are prime lenses (meaning they are a fixed focal length). People use zoom lenses for the same reason they use digital cameras and buy fast food: convenience.

The kit lens that came with your camera (any kit lens for that matter) is not that great. If you want to take close-ups, you're going to need a macro lens: a lens that is designed to focus close to a subject. The 70mm may magnify your subject more, but if it can't focus closer than 1.5ft, what's the use?

Lenses are where the real image quality comes out in cameras. My advice is that you save up and buy a high-quality lens for what you want to do. I'm not familiar with Sony's line of lenses, unfortunately, but if you research on www.wolfcamera.com or www.adorama.com or if you simply go down to your local Wolf Camera, someone will be able to help you pick out a good lens for what you want.

"Lenses are where the real image quality comes out in cameras"

Ritchie gave you a really good answer, I am just here to reinforce it, the lens is the MOST important part of most camera systems, and "kit lens" are usually not the best lens to use, just one to get you started.