Difference between Shadow and Lightning

[Otus]

Hello all and thank you for taking your time to read my post!

I'm a somewhat newer player and I got to max level with an assassin (love it). However, I can't seem to figure it out what the difference between Shadow and Lightning is. In each spec I can do the exact same things that I can do in the other one. All of the skills are alike, all of the synergies are alike, all of the combos are alike, all of the procs are alike. What's are the differences between them and why are they relevant? 

Thank you so much for your time!

[Ayanaye]

Hi,

in lightning build you deal damage in stealth. your main damage comes from heartstab-lightning rend anicancel. Lightning is considered more difficult, as many bosses have mechs or aoes that knocks you out of stealth and mess up your rotation.
In shadow build you want to be out of stealth most of the time. Your damage comes either from heartstab (shadow dragon) or heartstab-darkstrike (shadow tiger) while having 5 stacks of poison on the enemy. shadow is in general more easy to learn as a new player and less stressing in high level dungeons and raids.
Though lightning build has overall better dps, I personally enjoy the shadow build a lot. It also got a decent buff with the last patches and is very strong in longer raids. Shadow tiger build has solid sustain dps as well.

[Nivalias]

Aside from several minor thing, there is one skill that is fundamentally different between the elements. Lightning has "Lightning Pierce", which is used during Stealth Stance, while Shadow has "Dark Strike", which is a Decoy Stance skill. Lightning Sins need to put focus on entering and maintaining Stealth Stance to do DPS, whereas Shadow Sins don't need to do that.

[Otus]

I see, thank you so much! Is there anyway I could see the difference in damage between the builds? (Let's say, difference between the dps done in stealth while in shadow and while in lightning, as you can do both even if you are shadow or lightning)

[IAmWho]

Go to f12, put a random boss and dps it with the different build and compare your dps yourself