If installing both a heavy duty rear stabilizer bar and a rear trac bar yourself, you might run into a mounting issue.
The shop that installed our rear Roadmaster bar and rear Henderson trac bar back in 2007 on our 2007 E350, had a unique challenge, I recall it was something involving "shared mounting points". My point here is that you might run into a situation where the stock hardware may not work as designed. Plan for some time on the phone with one or the other companies on how to address it.
Again, that was 8 years ago on our 2007 E350. Maybe the chassis today, or the parts designed for them are different. I share this not to discourage getting both, but rather to prepare you for a potential hick-up.