The Logitech MX Master 3S and the Logitech MX Anywhere 3S share more than a name. Both record Bluetooth Low Energy and Logi Bolt connectivity, both record a battery life of up to 70 days on a full charge, both record a 10 m wireless range, and both descriptions record an electromagnetic scroll wheel. What separates them is the body: the Master 3S is recorded at 141 g as an ergonomic wireless mouse with a sculpted shape for medium to large hands, while the MX Anywhere 3S is recorded at 99 g on the product page as a compact wireless mouse intended for travel.
So the comparison is not really about wireless standards, because the recorded wireless figures are identical. It is about how much mouse a person wants to move, and where.
Every value here comes from the specifications recorded against each product, with the manufacturer page it was read from. No mouse was measured for this comparison, so there is no claim about tracking behaviour, scroll feel, or build quality beyond what is recorded.
What actually differs
Weight. The Master 3S records 141 g and the MX Anywhere 3S records 99 g on the product page, while its support specification records 95 g with the battery, a point the catalogue marks as conflicting. That is the single number that decides most purchases, because a mouse that travels gets picked up and moved constantly, while a mouse that stays on one desk does not.
Shape and hand size. The Master 3S is recorded as an ergonomic wireless mouse with a sculpted shape, and its description places it with users who have medium to large hands. The MX Anywhere 3S is recorded as a compact wireless mouse intended for travel, with no hand size recorded. A sculpted palm-filling body and a compact body are two different answers to the same question.
Buttons. The Master 3S records 7 buttons, and the MX Anywhere 3S records 6. The recorded feature list also puts multi-device switching and quiet switches on the Master 3S, while the Anywhere 3S records an electromagnetic scroll wheel and multi-device switching. More buttons means more direct control and more to configure.
Sensor resolution. The Master 3S records 8,000 DPI. The MX Anywhere 3S records 200 to 8,000 DPI on the product page, while the support specification records 400 to 8,000 DPI, which the catalogue marks as conflicting. The two are closer than the weight figures suggest, and the recorded difference between them is one of labelling rather than capability.
Surface support. The MX Anywhere 3S records support for glass and most surfaces. The Master 3S records no surface support value.
Size. The Master 3S records 124.9 by 84.3 by 51 mm. The MX Anywhere 3S records 100.5 by 65 by 34.4 mm.
Who should pick which
Choose the MX Master 3S if the mouse belongs to one desk, if your hands are medium to large, and if you want the recorded 7 buttons, the recorded 8,000 DPI sensor and the recorded quiet switches in a sculpted body that supports the palm. It is the choice for a fixed workstation.
Choose the MX Anywhere 3S if the mouse goes in a bag and comes out on a train, on a hotel desk or on glass, and if the recorded 99 g and a compact body are what you need. Its recorded support for glass and most surfaces is the specific reason it suits surfaces the Master 3S makes no recorded claim about.
What this comparison does not settle
It does not settle price, because no price is recorded for either mouse. It does not settle which one tracks better or feels better built, because no sensor figure beyond the recorded ones is available and no mouse was measured. It does not settle the MX Anywhere 3S weight or sensor resolution precisely, because the catalogue records both as conflicting between the product page and the support specification. It settles weight, shape, buttons, recorded sensor resolution, surface support, size and the shared connectivity and battery figures, which is enough to separate a fixed desk mouse from a travel mouse while acknowledging that the wireless side of the decision is already made either way.