This has been greatly debated in the past. The answer sort of comes down to what and where you want to hunt. Although either machine is capable of many of the same things, there are subtle differences which can give you an advantage given your situation. i.e. If you're going to go anywhere near saltwater, then the AT-Gold is not recommended as it apparently has a very hard time with saltwater environments (not that the Pro is much better, but functional) or the AT-Pro is a constant discrimination machine where the AT-Pro possesses a "true" all-metal mode, which can help when hunting those very small targets, or low conductors. There are also other differences, but first let us know what your targets and environment is and that'll help with advice.
FWIW.