Now I think everyone who like anime/manga knows what moe is by this point but not that many know what GAR is.
Gar like moe is a character archetype but unlike moe it has nothing to do with cuteness. It is all about being overly manly and badass.
The most obvious example of Gar is Tengen Toppa Guren Lagann super over the top manly action. But almost any show with a major badass could be considered GAR.
So which is better Moe or Gar? This maybe a unsatisfying answer but I all depends on what you like. If you like K-on or generally cute girls doing cute things is all you want in your anime then moe is for you. If you like shirtless men going into battle being super badass then maybe GAR is your thing.
Of course the two can co-exist.