Here's what I've heard on the carbon, ammo-chips debate:
Carbon isn't necessary unless you are trying to remove meds after treatment.
Carbon can strip the necessary trace elements that your tank needs to maintain it's health.
Ammo-chips are not necessary but if you have an over stocked tank they can be beneficial. Regular cleaning and maintenance are more of a benefit, but the ammo-chips will not harm the tank.
Now, my opinion:
Depending on which tank it is, I do run carbon, ammo-chips or Purigen.
For our 40g planted I use Purigen
For our planted BW, i use ammo-chips
For our 115 soon to be african cichlid tank I use carbon (fake planted)
For our planted 115 tetra/angelfish I use Purigen and ammo-chips. (I'm only running minimal filtration at this point, 1 Fluval 405 and a HOB
rated for 60g)
For our planted 20g long floss in the rapids mini-canister filters, ammo-chips in the UGF
tube outlet thingies
For our planted 10g shrimp, Purigen in the filter bags
For our planted 29g I run ammo-carb mix. Carbon in that mix because the fish in that tank (pair of always spawning firemouths) constantly dig everything up causing the water to cloud (yeah, even after cleaning)
For our planted 120 I run Purigen and ammo-chips
All our other tanks are on a case to case basis as well.