I was going to get a Coolermaster Hyper 212 Evo, but I think it would be a bit bulky for my mITX build. So I was swaying more towards a AIO Water Cooler such as the Coolermaster Seidon 120V. I am just unaware if this is a better choice, or if it is still better to go with the Coolermaster Hyper 212 Evo, they are both around the same price so the price doesn't really matter. I don't know much about water cooling, so if their is a better option please tell me
Cooler Master 212 Evo is not bulky. It will fit easily. If you can provide the PC Case info then it could be better checked. For miniITX build your preferable choice is AIO single rad with 120mm fan like Corsair H80i or so.