I bought two Silvers uMAx detectors as gifts based on the good reports I read.
I bought a Cibola for myself also based on good reports, some of those from Britain.
One of those Silvers is for my wife. In the Spring we'll have the chance to match them and see.
There is a lot of information available on this forum, the Tesoro.com forum and Treasuredepot.
Look especially for postings by Monte and Scully. Tabdog and Gunnar have worth while postings as well.
Heck, read them all.
See also the reports available from Britain. You can Google for those.
Either is a fine choice.
Tip: The Compadre is competent, underrated and relatively inexpensive. I very nearly bought one instead of the Cibola.
If a ground balance feature is important, because of ground mineralization conditions in your area, the Vaquero is a fine choice.
I have just come through the selection process. Working out what is appropriate for me wasn't easy. I didn't want to make a mistake. But you know, I think it's hard to go wrong. The operator's skill, determination and site research are as important. Anyway, most things are found within 8 inches of the surface.
Cheers, David at Edmonton