What type of plumbing do you have now and what shape is it in?

It is galvanized and is 40 years old. Currently I don't have a problem with a water pressure, but the problem may be waiting to happen.

3 years?

If you want the best return on the money, do the Granite....

Frankly, I don't think either one will give you a return on your money. Go ask three or four real estate agents and see what they say. Granite is a high-end material for higher end homes. If your home isn't in the high-end price bracket where granite or solid surface counters are expected, then your buyers will be more interested in knowing that there won't be plumbing issues down the road with defective galvanized pipes.

Personally, I love granite and wish I had it now, however, there's nothing worse than nice, new countertops stuck on old cabinets that should have been replaced....as for the 'just put new doors on' I've yet to see cabinets worth doing that to - by the time you start talking about new doors, it's usually when they're falling off, and the rest of the cabinet is on the way.

I know I'm probably a bit naiive and I've lived in very active markets, but the 'pipe or counter' question is rather cynical for me. True, many people's heads will be turned by cosmetic work, however, in the end, I'd much rather know there was new copper pipe in the walls - I moved from Australia where they haven't used galvanised for decades, and even then copper was often used within walls and inaccessible spots...so I'd much prefer to see the copper.

Maybe a new kitchen too?

Well, the type of people that visit forums such as this usually know about, and therefore value such things as copper over galvanized, but the majority of buyers make decisions based on surprisingly superficial stuff... like countertops. So if you think the galvanized will hold up for 3 more years, be cynical and go granite, BUT...

... As pjb pointed out though, no sense putting good granite on crappy cabinets, in fact, if they're water damaged or disintegrated, they may even COLLAPSE under the weight of granite! Also, as castoff points out, the granite has to be generally as "upscale" as the rest of the kitchen. No sense doing granite if you've got 1970s avocado appliances, or el-cheapo vinyl flooring, LOL.

PS: Is this a slab house, with the galvanized running beneath, and the copper replacement runs will go in the attic, or...?

My oak cabinets are in good condition. My previous owner replaced the cabinets 10 years ago and at that time, he put in the laminate countertop. So the granite countertop could go well with the existing cabinets.
My house is a single story ranch house with crawl space. All the pipes run in the crawl space.

In my experience selling my older home two years ago, most people seemed underwhelmed when told that all the galvanized had been replaced with copper. They were much more interested in cosmetics. Sadly, I'd have to recommend that you spend money on stuff that shows.

ten years isn't that new for a kitchen - are the countertops that worn? If you're going to spend on counters, personally I think it's unwise not to do the whole kitchen...unless the counters are really bad.

On reflection, the choice you are asking us is kind of, umm foolish. It's like comparing apples to oranges.

I agree, many people choose homes on stupid things like gold taps, and overlook other things..

However, somebody who replaces countertops and leaves gal pipe, is going to give the impression when they sell, they're doing cheap and nasty and may make people think you're covering other flaws up.

OR, to quote an old saying, penny wise, pound foolish. If one of those pipes fails in that three years - and, you never know, you may decide to stay longer - things change - you will be faced with potential damage and may need to remove those countertops to replace the pipes that should have been done, and the granite could well break in the process.

In the kitchen at least, the time to do the pipe is when the counter's off....so you should seriously consider doing both. There is really no logical answer to this question that makes sense.

If you want to sleep soundly at night, and feel confident you can go away for a few days, replace the pipes.