I started with a X-Terra 305 and upgraded to the 705, although I have since upgraded to the Equinox 800 I have no plans on selling my X-Terra, I like it that much. One advantage is the ability to change frequencies with different coils, there are also coils that have all 3 freq. If you target silver coins you can run in low freq., gold-high freq., and for general purpose detecting and relic hunting the mid freq. works really well. If you are in no rush to upgrade maybe keep an eye on the classifieds for a used 705, it may save you some dough in the case you like the 505 and will want to try the 705 later, I was happy with my 305 but curiosity about the 705 got the better of me and I'm glad it did, it was a worthy upgrade. The X-Terra is a great coin shooter, has very stable I.D on coins even the deeper ones, I think you will be surprised with it's performance. Good luck with any machine you decide on!