In the world of PCs, "gaming" tends to means "high performance", and that usually means higher power consumption. Poor battery life is just one reason why hardcore gamers tend to avoid wireless mice. Logitech thinks that those folks should give cord-cutting another chance, though. The company debuted its Hero high-efficiency and low-latency wireless mouse sensor last year with the G603 Lightspeed. Now, the G305 Lightspeed combines that same sensor with the classic shape of the G Pro, all at a lower price than the G603.
Functionally speaking, the G603 and G305 are almost identical. Both are wireless gaming mice with top-grade optical IR sensors and six programmable buttons. The primary difference in the two is that the G603 had optional Bluetooth (BT) support, while the G305 requires the use of a Logitech wireless dongle. In my reckoning, dropping BT makes little difference since that type of connectivity doesn't make sense for a gaming mouse. The special sauce of sensors like Logitech's Hero goes almost completely to waste when using Bluetooth and its maximum report rate of around 113 Hz.
By contrast, the Hero sensor inside the G305 supports a 1-kHz polling rate, much like all competent gaming mice. Alternatively, you can say (as Logitech does) that it offers a 1-ms report rate. That feature is critical for fast-paced gaming, and experienced shooter players will feel the difference right away. The G603 had a hardware toggle to swap between a high-performance 1-kHz mode and a high-efficiency 125-Hz mode. The G305 lacks that switch, but it's not impossible that Logitech's software will expose such a control for users who wish to really save on battery.
That's probably not necessary, though. Logitech says that the G305 Lightspeed can run for "around 9 months of typical use" on a single AA alkaline battery. That's very impressive performance from the Hero given its specifications. Comparing the sensor to that of Logitech's other mice and PixArt's finest, the Hero seems likely to be a heavily-tuned PMW-3389 unit. That's generally considered by mouse enthusiasts to be one of the best sensors around, with tracking performance that far outstrips the ability of any human to whip it around a mouse pad.
The G305 Lightspeed isn't available yet, but it'll appear in black and white finishes when it shows up later this month. You can preorder it directly from Logitech for $60.