Yours are worth nothing. Heavy weapons still need good stats to have value.
There are a few pros and cons about heavy weapons, and I'll go over the important ones.
Short Version
Pros:
1. Better looks
2. Slight increase in damage
Cons:
1. Prof gain is slower
2. Could be dangerous when running
3. Might be overkill at times
4. Price
Long Version
They attack at half the speed of normal weapons, but for double the damage. The advantage here goes to heavy, since the enemies armor only gets taken into effect once per 2 seconds, instead of twice per 2 seconds.
Another advantage is the looks. Obviously we all play LS for the killer graphics, so this is pretty much the most important thing ever. Seriously tho, the heavies generally look better, at least in my eyes.
A con would be you cant do any action for 2 seconds after hitting with a heavy weapon. If you need to bail, you'll have to wait 2 full seconds before the door will let you out. This can seem like an eternity when death is staring you down.
Another con, which I think is complete bullshit, is your proficiency gain is based off of number of attacks, no matter what weapon you use. So basically you gain profs at half the speed. This really doesnt make any sense to me at all, but neither do a lot of things in this game.
Overkill is a con too. In arena this was fine, but in cata when you need to switch targets, it could slow things down.
Price is a huge disadvantage too, they cost a lot more
Heavy weapons had a huge advantage in Arena that most people didnt realize. Its not worth trying to explain since its gone, and since most people didnt get it anyway.