I'd lean towards the UA/Shadowburn more, as it gets you some more firepower in the right direction.
For grinding and farming (and raiding) you're lookin at runnin around with your Imp out, where Demo's stat boosts help a lot, but Fel Domination, Improved Healthstone, and Improved Imp are only going to be minor boosts here. Demonic Aegis is actually one of the better things you picked up there for either a Fear rotation or a Drain Tank rotation, but even that isn't a huge boost to anything. The good thing here is I assume you're already very comfortable with your pets and with the Fel Domination ability, so I don't doubt you could get some nice PVP off with this build.
On the Destro side I'm digging mostly the Shadowburn and Bane, as well as Destructive reach allowing you to pull some nastier targets in with either a SBolt (has Projectile flight time so it's essentially free unengaged Dmg) or an Immolate (which nobody uses primarily because of the lower reach.) I would actually stick with the Shadowbolt. Of course Shadowburn will help you tremendously in PVP, although I don't really see it helping regular PVE that much since with that much Affliction you can handle an ungodly amount of monsters without a sweat. For Raiding and 5Mans you'd obviously be sticking to the DoT rotation + SB spam which this build would definatly serve better than the Demo one.
You can play a ridiculously good level 70 with 41/0/0, so honestly it's a question of would you rather be able to summon a Demon out quicker, or have a flash damage spell that could come to save your butt in some PVP. Think about how you'd rather handle a really nasty situation and base your choice off that.