Hdc1080 I2C connection to Uno

Ive seen both connecting to sda and scl pins on the uno (the ones next to aref) as well as to A4 and A5.

Which is considered the best option and why?


There is no best option, use either.
On the Arduino board, there is only one I2C bus.
The SDA pin is connected to the A4 pin, and the SCL pin is connected to the A5 pin. If you have a multimeter with a continuity tester, then you test that those pins are connected.

The SDA and SCL next to the AREF pin were added for the shields (add-on boards). For examle the Arduino Leonardo has the I2C bus on other pins, but both the Uno and the Leonardo have SDA and SCL next to the AREF pin.

Older versions of the Arduino Uno did not have those extra SDA and SCL pins next to AREF.