Jehovahs Witnesses claim to be happier than non-Jehovah's Witnesses.
Jehovah's Witnesses claim to be happier because they live in a spiritual paradise where everyone is more loving and more moral.
One of the reasons I left is very simply because I found these two claims to be false.
I disproved them by one simple action; getting to know non-Jehovah's Witnesses. The more I did this, the more I found that happiness and kindness were traits that were not associated with any particular religious, social, business, ethnic or political group. Happiness and kindness instead were associated with very individual qualities: self confidence, good naturedness, humility, generosity of spirit and patience, among others.
I continue to try to apply these traits to my life and study those around me who display these traits. I think this is the way to happiness and indeed I also believe it is the way to god.
take care
Joel