They both were just released. Neither is "newer" not that that means anything.
The 840 pro would obviously be faster, but will cost more. The 840 is more targeted at consumers. Our you can just pick up an 830 on sale. 256GB ones ate going for $160.Http://lmgtfy.com/?q=Samsung+840+vs+840+pro
so if i choose 830 , what is the difference between 830 and 840 pro ??
and also if found these on newegg
SAMSUNG 830 Series MZ-7PC128B/WW for 98 $
SAMSUNG 830 Series MZ-7PC128D/AM for 129 $
so why that big differences in costs?