Pete
Welcome to Aussie Pinball,
Out of the machines that you said either Whitewater or Fishtales are both excellent first game titles and you will have hours of fun with any one of them. Then its get a second pin time because you can't just have one pinball machine.
You will soon realise this once you have got your first pin, and then it starts, once you have been bitten by the pinball bug, you will always have room for one more pin.
Good luck on tracking your first one down and if you need any pointers just ask away on here and you will always get some good advice from the guys on this forum.
Darren.