It is diffirent.
Pleasure trough pain allows you to play more flexible. Cast time reduction for shadowbolt alone is a good thing. Simple example, you cast your shadowbolt with 2 second cast, your imps will cast their Firebolt with same speed. If you pick Pleasure trough pain, your cast time will be reduced by 0.5 seconds, while imps will retain their original cast. This allows you to more fluidly gain shards, summon imps via HoG and be always few seconds ahead of your imps before you’ll be able to cast implosion or Tyrant.
Another good thing with Pleasure trouhg pain, is that she increases ALL shadow damage you do to the target. It is your Shadowbolt, demonbolt, Hand of Gul’Dan, Implosion, Bilescorge bombers…additionaly it is increases damage of trinkets that does damage with shadow - Forbidden Obsidian Claw as an example. Additionaly talent increases Succubus/shivarra’s damage of Lash of pain that also deals the shadow damage. Talent also works with Twisted Appendage.
As for gameplay, the nature of Succubus abilities will force diffirent kind of talents from you to use, and slightly diffirent mindset. In one hand you’ll lose aoe and cleave damage from felguard, in another Succubus absolutely ignores armor of target with her attacks, additionaly she could give you so much more damage from other sources.