What's your local tap water like. I'd be inclined to use that as a guide as which to go for. You are talking about two very different types of water. If you've go soft acidic water I'd go Amazon, if it's hard and alkali I'd go African. In the middle, then take your pick, personally I'd go Amazon, as I think the fish are much more interesting.
The real deal is that none of these fish are particular about ph, unless it's really far one way or another. I can tell you what I like (both) but it won't help you decide what you like. Even among the amazon/african options you have a wide range of very different choices - it all depends on what you like and what you're looking to accomplish with the tank.
What size tank is it? Are you looking for an active tank or relaxing tank? Crowded or sparse? Small fish or big fish? Do you have decor in mind or are you going to plan according to the fish you get? Is color and markings more important, or character?
Just with the last two posts you have two extremely opposite types of tanks, and both are legitimate recomendations, and both are not for everyone.
I'd go with african. Just use baking soda every time you do a water change! Plus their colors and attitude really win you over. And it's a nice change to the 'planted amazon look'.
Of course this is only my opinion, do whatever you want!