I'm wondering what Cho'Gath Build is better, AP or Tank? Tank Cho'Gath doesn't seem to go well for me... AP Cho'Gath nearly got me M7 with 'em. You're welcome to post your thoughts as well, though my preference is AP Cho'Gath. :) 
and 
is my Build, btw.
Tank Cho'Gath is my preference. The raw amount of health he can stack with his ultimate combined with high resistance items such as thornmail make him arguably the tankiest champion in the game when fed. And due to his ult's health scaling, he can still hit quite hard even while building tank.
Well if you have much more success with AP, then thats what you should go with. I go tank because you don't need to stack AP to delete people, and building AP is more risky since your spells are dodgeable. But really, you should do whatever works for you.
AP Cho'gath is better.
Why?
Cho'gath lacks the traditionally short cooldowns and reliable crowd control to actually function as a tank. He cannot engage like Sejuani, Malphite, Amumu, Zac, Leona, Braum, Ornn or even Rammus, and even with his E and his Stoneplate + Feast combo he usually does less damage than most of those champions. If he does not get fed enough to one shot with Feast, his target will survive and Cho'gath will be useless for the next minute. He lacks options to peel for his allies, which is extremely apparent when compared to champions like Galio, Maokai, Braum, and Poppy. To make matters worse, he is incredibly easy to kite, and, sadly, even with high resistances, his infinitely stacking health does not matter thanks to the plethora of easily itemizible % HP damage in the game. There's also the problem of where to lane tank Cho'gath. If you take him top, you likely have to run Teleport, but Cho'gath has relatively little ability to make use of the Summoner Spell thanks to his poor options in ganking with it and his fairly weak splitpushing. If you run Tank Cho'gath in the jungle, your team has little to no early pressure, and Cho'gath is denied access to a better gold stream. If you run him mid you have denied your team of a more effective source of damage, utility, and waveclear. He also does not roam very well to assist other lanes.
While AP Cho'gath still has some of the same weaknesses, he has less overall and has greater strengths. For example, the monster mage's large health bar becomes an asset to protect him from assassins and burst damage rather than a liability for your team as a result of an enemy's Blade of the Ruined King. As AP Cho'gath itemizes more mana and fulfills a different role on a team than a Tank Cho'gath, his Q and W can be used more frequently and are less punishing to miss. AP Cho'gath has an easier time fitting into a team composition, as you are able to play to his strengths, rather than trying to make him something he is not.
Tank, but you don't play him like a Tank at all. You don't initiate or try to CC someone like a Tank, you just use your immense health pool to survive through everything while you snowball ahead with the infinitely scaling damage on your E and R and the health scaling damage of R. Q and W are mainly just for additional disruption or to make you have some use when behind.
This is typically the build you have for Cho'Gath with each item having an obvious purpose. As Tank Cho'Gath you basically have to perfect the art of being a sneaky Godzilla that does as he pleases. Outmaneuver the enemy at all times.
I'll ask my roomate - who mains Cho'Gath - what he prefers and let you know what he tells me.
Damage builds will get you to higher mastery levels because their feast-or-famine nature means the games you win will be more likely to grant an S.
Has good AD ratios and works well with Lethality because of her %health damage, but she still wins more often as a Tank. It won't be as flashy and it won't give an S nearly as much when it does win, but it wins more consistently.
I prefer to go tank cho'gath jungle, i can carry most games i play (considering im not fighting kayn/yi or other tank shredders, however adc's are beatable thanks to the immense slows) i like to use hail of blades to get my E off quickly and to get close i land a q, which good cho mains know how to do and once that happens a quick qw combo ensures they cant move or cast abilities for a long time thanks to knock up and silence, their also issued a big slow and then the health means they cant beat me easilly, the build i use personally is titanic hydra thanks to it's % of my health as damage, then i use warmogs so i can trade well, then i go gargoyle plate so i can basically increase my ults damage significantly, which combined with blue cinderhulk, i can have the extra 20% health from cinderhulk + the extra 40% from gargoyle, also the R is true damage, so it's damage cannot be altered by the damage reduction from gargoyle, so i hide in a bush, say a ahri where to face check it, i q under myself, then w as the ahri lands (maximising the "silence") and then discharge my E with hail of blades (note that hail of blades increases damage and width with size and stacks with 0.5% of their max health per stack so basically you SHRED them) and activate the hydra while using the e, meaning i do 10% of my health ontop of the E, the R + gargoyle means that your a 10k+ health tank with over 100 mr and armour AND you do like 1.5k dmg with your ult if you build full health. my normal build consists of : titanic hydra, gargoyle stoneplate,frozen mallet (for extra slow with the E and for basic attacks + ad and health, whats not to love), warmogs, dead mans plate/spirit visage so tankshreds like BORK and liandries do less dmg. against certain picks like yasuo this works great however i normally trade the spirit visage for randuins omen in that situation. the dead mans plate helps catch those mages and adc's. nothing is more fun then one shotting with cho'gath.
I build him both ways. Either i go r.o.a or pro belt first. Or if i have a tough match up top I get armour or mr first then go with a few ap items. I think cho needs some bit of tankiness to be fully effective. I usually always go warmogs and gargoyle s.p. to get him huge and by that point his ult is deadly
I'd also say Tank Cho. Also I generally go Resolve/Sorcery for me and this is usually what I'd pick for other runes...
Resolve: Grasp of the undying Demolish Conditioning Overgrowth (Or go Second Wind if you playing him top against poke)
Sorcery: The Ultimate Hat Transendance
Personally, I think sorcery is really good for him since ultimate hat + max CDR can lower his CD of his ultimate to like 32 when it's maxed and Transcendence is very good on him as well since I usually build 
on him anyways so it's very easy for him to reach max CDR so why not get some AP out of it as well. Though you could replace transcendence for Scorch for the lane phase trades, or Gathering storm if you plan to stall out to late game.
i like support cho, since you can go font of life and revitalize as well as a knights vow, face, and locket and make one your entire team hard to kill with all the heals and shields that scale with your hp and it only gets better with gargoyles
