I’d guess that the truth lies somewhere in the middle. I suspect that when both halves of a couple are living the lives they want and are in agreement about how their household should be run, a happier relationship and better sex is the natural result. If your dream is to be a working mom, and your husband supports that and does his fair share around the home, you’re both probably feeling pretty good about your individual lives and your relationship. If you both feel that one parent at home is the way you want to live your life, ditto. It’s when desire is thwarted—when mom (or dad) is unwillingly out of work and doing more household duties, or when one parent is working when they’d rather stay at home—that the relationship is likely to take a hit.
Like this story indicates, when women get what they want, whether it’s working or staying home, the whole household benefits. The same holds true for men. A household is an ecosystem, and if one partner is overburdened and unhappy, the relationship is going to fray. No one needs an academic study to confirm that.