From RadioMail’s perspective, the BLE interfaces to the BTECH UV-PRO and the B.B. Link adapter are functionally identical. They both expose a KISS TNC.
The practical differences in your setup come from the packet TNC modem implementation (AFSK modulation, packet decoding, buffering, etc.), as well as the radio hardware and antenna.
Assuming features such as Roger beep and squelch tail elimination are disabled on the UV-PRO, any remaining variance might simply due to radio performance.