Same basic builds, only difference is the hard drive. One would be a 256gb ssd (faster opening of programs, faster booting but less space and more expensive), the other uses a regular 7200rpm hard drive with much more space at half the price. Probably still plenty fast enough for the work he does and would still be a lot faster than his old laptop. Cases are sort of personal, you or he may not care for the case I picked it's just a suggestion. Not sure if he needs a mouse and keyboard as well, but it includes win 8.1 in the parts list. For filing tax returns or accounting, the i3 should be plenty fast enough. It has integrated graphics, enough to handle office software and online videos or dvd playback. He shouldn't need a fancy expensive graphics card for that. Got it down to $440, so even if he needs a keyboard and mouse it will keep it under $500 to add a decent office mouse/keyboard. I've had good luck with microsoft and logitech for inexpensive basic mice and keyboards.