The spec line of cases aren't bad in terms of looks although when I started comparing specs of various cases opted to pass on it. I prefer to use air coolers over water coolers and the spec 01/02/03 cases are a bit narrower than most other cases with support for cpu coolers up to 150-157mm. Unfortunately that can really limit the options, many cases offer at least 160mm clearance for a cpu cooler. Even the popular budget hyper 212 evo is too tall to fit in a spec 03 case.
Some cases may have a better design for airflow but it's kind of a personal choice in terms of looks and flexibility (removable drive bays, fan mounting options etc). A lot of people like the phanteks enthoo cases, as well as fractal design r4/r5, nzxt h440, corsair...