taternut,
The GB Pro is the only detector I've ever used and I've only had it for 4 months so I'm not nearly an authority on detecting. However, among the many factors involved in choosing a detector, the geology and the occurrence of gold in a given area should be taken into consideration. I have read the geology books, biked the trails and hiked all around our area of Northern California and have found that this area has experienced much erosion, leaving plenty of shallow and exposed bedrock which is great for the GB Pro. On the downside, I am finding that this same erosion has filled gullies, washes and other waterways with auriferous sediments that have ultimately been too deep for me to detect. More experienced detectorists in this forum have suggested that the 10" elliptical coil is more capable for the often deeper and more course gold that occurs in our area and for this reason I'm looking into getting the larger coil. There are many tricks you can learn to find gold with the GB Pro in this landscape, and I have detected some nice pieces. If you decide on the GB Pro, see if you can swap out the 5" coil for the 10" elliptical, even if you have to pay a bit more.