Airflow is the single most important aspect of any case. OC is just a hobby, really doesn't improve the pc ability much, but heat has a huge impact on ability. Cases with good airflow ability stay cooler on the inside, this means you get cooler air surrounding the cpu/gpu heatsinks. This allows for changes when you do push the cpu/gpu hard, even with apps for rendering, cad, production etc. But much must be taken into consideration, as in user taste, some ppl just don't prefer the classic boxy looks of the pro-m, the H440 looks 'better'. Some even think the H440 is still too plain, they want the over-the-top looks of some of the Apevia X-Gamer series. So your opinion is quite understandable. Maybe a good balance might be the nzxt Phantom 410, which has the gamer look, yet has outstanding airflow properties and is also on the same quality of build as the H440/Pro-M.
In the end, it is your choice, you have to look at the case, we don't, but apart from looks it's also good to find a case that fits you, your needs, wants, aesthetics, personality etc. Kinda hard to justify a case that looks great, built great, but only fits a 154mm tower and you've got a 160mm hyper212, or only fits a 240mm aio as intake and you want a 280mm on top.