People use hope because of its perks and high damage at close range.I just dont click with sidearms (yet). Something seems off about them, like Bungie is screwing with them behind the scenes. Plus, they simply lack too much range for my tastes.
I think people use Hope with VW only because they cant use anti.
As for sidearms, they're pretty simple. Get into say...Acrius kill range and hipfire. Aiming down sight is the mistake people make with sidearms. That range is where most combat in Destiny PvP happens unless you're intentionally trying to avoid any close range combat (which is hard to do given the size of most maps), so they are very effective in this patch. Just gotta get used to getting in closer than you probably do in regular combat, bro.
You will slaughter with the better 3-burst and full auto Sidearms in particular. I'd recommend spending time with:
// Kinetic
Last of The Legion
Peace By Consensus
Enigma's Draw
// Energy
Etana SI4
Swift Solstice
Traveler's Judgment
Last Hope
Just spend time with them until they click. When they do click, whooo boy.