Why does my voice sound different on a Blue Snowball vs an IPhone built-in microphone?

My voice on the iPhone mic sounds more light and agile, but on the Blue Snowball it sounds deep and heavy. I haven't adjusted settings for the Snowball yet, but should I? Is the iPhone mic true enough to trust as my standard?

Yes

The microphone in the iPhone is much less of quality than the Blue Snowball. The difference your hearing is the quality of the microphones.

A condenser mic like the snowball produces the full frequency range. The iphone mic (and pretty much any phone mic) cuts out the low frequencies to enhance voice quality. Pretty much any studio mic will sound bassy compared to the 5 cent mic they put in your phone.

If the recording you are making is TOO bassy with the snowball you can always adjust the sound with the EQ built into your recording hardware or software.

BECAUSE THE SIZE OF SPEAKER OR THE QUALITY OF AF AMPLIFIER CIRCUITS ARE DIFFERENT, ALSO MICROPHONE QUALITY ARE NOT THE SAME, THAT MAKES THE SOUND DIFFERENT.

Different levels of engineering
The blue is more of a pro piece of gear, as the iphone one is consumer gear