there is a report on another form done by Jonathan Porter the new 45 ground balance quicker run quieter and are very stable. I look at it this way the 45s have been around for many years may be 12, over that time there would have been upgrades and the same with the 5000 some put the 2 together in the new release of the 4500 and you have a very good detector for the money ,with the difference price between the 45 and 5 you can buy some new coils ,new detector new coils you are on a winner regards john :Y: