I would say hands down 2H bg, it is the strongest 2H option on destro, yes im DE biased but hear me out;
You want a damage class that can still help your team, so you need to first ask your self, what is your purpose are you goint 2H for? To give up your shiled you lose a lot of things, such a surviveablity from block and powerful tools like Chosens destined for victory tactic or BG's 5s KD and utlites like Hold the Line!
In return for losing all that you trade it for a certain form of utlity or ablity, you play a certain role.
So the question is what role can you play as a 2H chosen vs a 2H bg
2H chosens role is to apply Crippiling strikes in an AoE by using Rending blade, Its a role more oriented toward oRvR/WB play, and this role was recently ruined by the devs becuase they didnt like that CS stacked with challange so they made CS single target only I.E blast wave and rending blade could not apply it in an AoE; however, the devs say thay will bring it back at a reduced value so not 25% but rather 10% or something, overall it will be weaker and i (personally) feel that 2h chosen is only good for if you want to have style points now as while chosens SnB build has always been the better option, it is even more so the case now
2H bg's role centers around the use of crimson death, applying the AoE 10s Crit debuff which benifits all allies and the BG as well, additionally BG has both great Damage and surviveablity, Crimson death has one of the highest tool tip damages in the game, you can crit a lot thanks to filled with fury and when you crit you can remove 1000-1200 hp from a target due to hastened dooms wounds debuff, from there you can slot parry and toughness tactics for survieablity and and even more tankyness with Force of fury or go full dps/caster killer with soul killer for a no cool down outgoing heal debuff, which when paired with an mdps inc heal debuff can debuff a casters healing by 75% + you reduce their healing even further by debuffing their will power and unending fury lets you ignore all detuants
all the while having all the cool tools that bg has like super punt etc
Also thanks to the devs 2H bg has access to to a reliable knockdown with a 2h so its a very strong playstyle option now
2H ib plays a completely different role than 2H bg, while 2H bg trades a sheild for more offensive power with crimson death
2H ib gets a 2h for a reliable KD, the shield kd is 10s cd but requires block, 2H kd is 20s cd but on demand, while it might seem like a small reason, IB is an other wise solid class with good survive and great buffs that makes it still an all around good tank