I have never used henna so I voted for color rinse. I use any color by jazzing and my hair is so shiny and strong. I use them after a fresh relaxer..after i neutralize but before any other shampoo or conditioner andI get great results.
I think a draw back for some would be the fact that washing/rinsing frequently will rinse the color out quick and I protective style alot so when their is lots of product (moisture) in my hair the color can stain my pillow cases depending on what color I use.
I only put the color rinse in my hair after I relax because I wear my hair down/wrapped a few weeks after the relaxer then its up under a wig until my next touch up (12+ wks).
I don't have much experience with rinses. The kind I've tried won't stay on my hair which is what led me to henna.
Henna
Pros - it conditions and colors. You can use whether you relax or do bkt's. It's a natural herb that you can use as much as you like with no negative effects.
Cons - it's not a quickie treatment and it can be messy esp. if you're new to using it. You only have one basic color choice - i.e. red. You can add things to make it darker red or red brown but basically just red.
i use henna/indigo one week after relaxing. i have used color rinses in the past (and only once since i started my HHJ) and prefer henna because it is natural and less drying. the only negative i have with henna is that it is time consuming (day long process). but the end results are worth it.