If you are hunting in trash get the regular coil. 10 inches is way to big for hunting in trash even if it is DD. I think you would have a better chance with the narrowing cone on the CC coil. In trash I would want a 8 inch coil. I don't think the X-Terra has one. You will probably end up getting a 6 inch coil for trash and a 9 or 10 inch coil for depth. When I bought my 305 two years ago I though I needed more depth. When I got the E-Trac 18 months ago I realized what I really needed was separation to find silver coins in junk! The 8x6 coil on my etrac offers me the depth and separation I need. I almost never have to change coils.
I think I would rather have the 705 than a Gold Bug, but if someone gave me a gold bug, why would I even need a 705? I consider them similar tools! For a second detector I would get a Compadre, an F2, an Etrac, CTX, Excal, Sovereign, ATpro, or something dissimilar. Really the ATPro is kind of similar, but atleast it is waterproof.