What the numbers mean
These two are the most common "first serious thermal" shortlist, and they share more than they differ: a 384×288 sensor with 12 µm pixels, IP67, a swappable 18650 battery, Wi-Fi to an app and a 5-year warranty. The gap is in the lens. With 19 mm against 15 mm, the Taipan recognizes a coyote at about 200 m by our calculator, the K3 at about 155 m.
The K3 answers with weight (0.47 lb listed by RIX against 0.31 kg plus a cell for the Taipan), electronic image stabilization and a wider 17.5° view. The Taipan has the better screen (1024×768 OLED against 800×600) and a second battery in the box. If the $396 difference matters, the K3 is the smarter buy for close cover; for mixed ground, the Taipan earns its price.