Giovanni's Pros
Great for cleansing an oily scalp
Feel-good tingle
Affordable

Giovanni's Cons
Can be drying to most hair types


Trader Joe's Pros
Great cleanser
Feel-good tingle
Cheaper than Giovanni

Trader Joe's Cons
Can be drying for some hair types

These shampoos are so similar that for some people it's almost hard to tell the difference. They both stimulate your scalp, smell fresh, and may help with flakes.

In my experience Giovanni's shampoo cleans my scalp better. I have to use more of the Trader Joe's shampoo to get my scalp clean. Because of this, using Giovanni is a better value for me.
I like to dilute Giovanni's shampoo a little because it is a tad thick. It truly lasts longer for me than Trader Joe's version.
If you don't have a scalp with a lot of build up from oil, sweat, etc, then Trader Joe's version would be sufficient for you (and it is cheaper than Giovanni).

Bottom Line:

Use Giovanni's for a deeper clean. If you don’t need a deep clean then Trader Joe's is fine.