The Explorer/Quattro is excellent on most medium size to nickels, small gold rings, earrings etc.
The Sovereign BBS circuit seems to have a bit better signal/depth on the smaller rings, particularly the Sovereign GT, but they are close.
The very small shards of aluminum, foil are also ignored and the silky smooth circuit (less noise) also allows one to hear a 'good signal response, however slight, since the audio thresholds on Minelabs run so smooth and they enjoy magnetic power line noise reduction on their start ups.
On thin band and gold chains w/o big pendants attached, the 1.5 kHz FBS circuit just won't respond to these targets with any signal.
The CHAMP as I see it is the Tesoro Tejon @ 17.5 kHz, with honorable mention to the White's MXT/M6 DFX (15kHz selected), Tesoro Cibola, Vaquero, Compadre, & Tiger Shark).
I've tried the Fisher CZ Series which are dual freak units.... they don't respond to my smaller gold jewelry chain samples in spite of incorporating a higher frequency like the DFX, but unable to select that higher frequency alone, so the voltage is split.