My iPad 12.9 6th generation consistently drops wifi

As a diagnostic tool, try installing the Apple AirPort Utility App, from the App Store, on both your iPad and iPhone. While this App is primarily intended to used in managing an Apple AirPort Router, the App has a useful WiFi scanning tool:

https://apps.apple.com/gb/app/airport-utility/id427276530

Once installed, you’ll need to change a setting on both devices to enable the scanning tool:

Settings > AirPort Utility > WiFi Scanner - set to ON

Launch the AirPort Utility App on both your iPad and iPhone - then tap the Wi-Fi Scan button at top-right of the screen:

Drag the Scan Duration slider from Continuous to something in the range of 20-30 seconds - then tap the Scan button:

When the scan completes, you can compare the measured RSSI values and channels. If these substantially differ between devices that are in the same location, something may be awry with the device hardware.

Are both your iPad and iPhone connecting to the same WiFi Router - using the same WiFi Band/Channel? If one is connecting via a 2.4GHz WiFi Channel - and the other via 5GHz Channel - you may see different WiFi performance at the same location.