In terms of what Chainer can loop, the big thing is any ETB/LTB triggers when combined with sac outlets. GloriousGoose listed some of the best, other nice ones include Gonti, Lord of Luxury (want counterspells? hit the blue player), Bone Shredder (conditional, but self sacs which is really useful) Agent of Erebos (you don't want to exile yards but sometimes you have to), Massacre Wurm (stack the -2/-2...), even just things like Solemn Simulacrum for the value. Plus there's also whatever is in your opponents' yards. When something like a Reclamation Sage gets killed/milled, it gives you a lot of extra flexibility when you can repeatedly get the ETB at instant speed. Building with a focus on ETB abuse - almost like a black equivalent of Brago or Roon - is something that Chainer can do well rather than just being a more traditional reanimation deck. I run Panharmonicon in my list for this reason.
Also, being mono-black makes it easier to produce large amounts of mana (Cabal Coffers, Crypt Ghast etc.), thus letting you use the ability repeatedly.
That said, I'm coming at this as someone who's been playing Chainer for over 3 years now, and am nowhere near being bored of it, so I'll obviously be cheerleading for him. TSG does have some very good upsides though, and as you point out, you get access to some great blue cards.
I think Chainer is definitely the stronger card in EDH where turning utility creatures into 4/4s is less relevant, but TSG does give you access to another colour. So, I guess it comes down to how much you value having blue.
Chainer, Dementia Master - cheap, repeatable reanimation that targets everyone's 'yards. You've got a clear strategy of being graveyard-centric and wanting lots of black mana (and maybe a bit of lifegain), but there's so much variety in how it actually plays out, as you get to play with your opponents cards, as well having as how you work to enable his ability (personally, I like removal as my main means of stocking graveyards but pushing heavier on discard and/or mill effects are options). And if you're looking to push the power level up, he can be an excellent leader for a stax/resource denial deck, as his ability can be a real parity breaker.
edit: I missed the later post where you said you had a Scarab God deck. Ah well, Chainer is still great fun to play
Also, being mono-black makes it easier to produce large amounts of mana (Cabal Coffers, Crypt Ghast etc.), thus letting you use the ability repeatedly.
That said, I'm coming at this as someone who's been playing Chainer for over 3 years now, and am nowhere near being bored of it, so I'll obviously be cheerleading for him. TSG does have some very good upsides though, and as you point out, you get access to some great blue cards.
edit: I missed the later post where you said you had a Scarab God deck. Ah well, Chainer is still great fun to play