I'm still reading, watching, and waiting myself, but as you said I'm seeing mixed reviews so I continue to watch...
As far as BBS versus FBS on certain beaches and even mineralized land sites, I'll just say on my mineralized beaches and on my mineralized land sites I prefer BBS for certain reasons. Rather than tell you why, I'll just tell you to search the FBS forums as well as this forum for those who own both BBS & FBS and hear what at least some of them have to say. Two of the topics they talk about revolve around stability/smoothness and thus depth in certain mienralized soils/sands, but there are a few others such as the quality or "robustness" of the audio on certain objects at depth such as gold rings. I'm not telling you who, what, when, or where in terms of BBS or FBS or giving you my open opinion. I'm simply saying search and read for yourself and make your own mind up.
Search those forums for Sovereign, Excalibur, Beach, gold rings, BBS, and so on and read and form your own opinion. Some say one thing, while I'd say more say another that I have experienced myself. Also search this forum for the FBS machines as some have voiced those opinions here as well. Just recently (maybe a month or two ago) there was a guy discussing the Ultimate 13" coil on his Sovereign who bought one and built a clone of it himself. He had some very interesting things to say on this topic, and it's not the first time I've heard this, and it jives with what I've experienced *in my soil and sand*. Maybe it's not the same for others everywhere.
For water hunting up to my belly button I just chest mount my GT and away I go. It was designed for that, thus the long coil cables. For divers the Xcal is dive raited while many other machines out there are not. When you're water hunting it's pretty much hear and dig, so I leave the VDI off my GT for that, and Xcal users just need a few simple controls to get the job done. Beyond sensitivity and threshold adjustment there really isn't much more needed. In fact, for land hunting that's all I really need too. All I really care about besides raw depth and good long/detailed audio with tone alerts for unmasking and such, is a good high resolution VDI, and the GT has that. Sure, the 10" Tornado does a great job at left/right separation and depth. Probably the best large DD coil in that size I've ever used in those two respects, until along came the 12x10...and made depth and separation even better. I'm a happy camper myself until I see something come along that drops my jaw in better depth/separation. Still waiting for that...