I love playing tank Cho. I usually go for Boots, Warmog's Armor and Force of Nature before customizing towards the enemy team.

In some situations I'd like to add a little more offense. I'm aware that Cho has nice AP scaling abilities and also the way I play him he usually has a lot of HP. So, which is better? Atma's Impaler or some AP boosting item in this scenerio? If AP is better, which should I go for?

I like going the AP route, and get a Rod of Ages. You get more mana, which is always helpful, more HP, so it's even harder to drop you, and the extra AP makes Feast ganking easier, as well as making you hit much harder with all of your spells.

Definitely the AP route. I'm sure if you've spammed your abilities you've found problems with your mana; Rod of Ages gives that, as well as 80 AP and HP; it's a great tank-AP hybrid item. Another good choice is the Rylai's Crystal Scepter. While it doesn't offer mana or as much HP, the slow works with all your abilities (even vorpal).

Lastly, if you're in need of more magic resist, the Abyssal Scepter offers a fair chunk (50 something?) while offering lots of AP as well.

Roa followed by a 2nd warmogs and then atmas or banshees instead of 2nd warmog depending on team dont forget quicksilver sash negates vlads ult

Get Hextech Gunblade. U will destroy the lil cho' with is RoA and nearly everything else

All the above posts are terrible.

Cho gets so much HP from his feast that building more than the HP Sunfire or Banshee's gives you is a total waste.

Go for Glacial Shroud / Frozen Heart, Banshee's, Randuin's, or FoN (after Banshee's if you still need MR) instead of Warmogs.

Cho's strength lies in his high base damages and CC, not his AP ratios. Don't build any AP at all if you're going for a tank build. Your AP won't be high enough to make a difference because you absolutely NEED resistances.

If you feel like you're not doing enough damage.. then.. well, you're not supposed to. Feast the carry next time and watch them explode.

Tanky AP stuff works well. RoA, Rylai's, Abyssal Scepter are all good items to add a bit of punch at the same time as survival. Add those to a couple of tank items... HoG/Randuin's, FoN, Thornmail if they have lots of physical, you know the drill.

Warmog's/Atma's is good for a laugh in randoms, though.

I've built Cho both ways before and am now on a tankish AP Cho kick. I find AP Cho much more satisfying as you deal much more damage than just pure tank. I usually go Doran's Ring, boots, RoA or Abysmal, then the one that I didn't get, upgrade boots to merc treads and then go for a Hourglass or Deathcap depending on the opposing team. From there its your choice of defense items, I go for Frozen Heart or BV.

Never understood the love for warmogs,you get much more effectiveness from other defensive items due to your innate high HP.

Cho'Gath is a prime example of the type of champion you should pretty much never consider Warmog's on.