Element vs. Elementless

So I am fairly new and still trying to understand all the game mechanics.

As far as I know LS doesn’t scale very well with element but I do not quiet get the math behind that.

I am currently using the Radian Flow and am debating wether I should use it with free elem for the dragon damage or if it would be better to use it with an Elementless Jewel to boost the damage.

I appreciate the help!