Most mice pick two of wired, 2.4GHz and Bluetooth. The SC660 does all three in a 77g shell with a PMW3325 sensor, which is the same sensor family used in far more expensive boards. The receiver stores in the underside of the mouse, so it cannot be lost in a bag, and the shell is translucent so the RGB is visible rather than trapped behind an opaque shell.
The one that goes between the laptop and the desktop without a dongle swap, and the one I reach for when I need Bluetooth rather than a receiver.
The PMW3325 is capped at 10,000 DPI and polling tops out at 1000 Hz, so it gives ground to the G Pro Wireless on anything competitive. The 500 mAh battery is small, and the RGB drains it faster. It is also the least refined shell of the four — the transparency is a novelty that wears off.