User blog comment:Kartik "k2"/Comparision between regular shinigami/Hollow and Vizards/Arrancars/@comment-493809-20140918152916

Skills and the particular type of power make a difference. While a Vasto Lorde may have more power than the average captain, the captains have experience fighting Hollows and a variety of abilities to back them up. The shinigami use flash steps, martial arts, and magic in addition to their zanpakuto. Conversely, hollows have a limited pool of shared abilities and techniques, most based on their nature as hollows.

The main trick is the individual ability each one has - most captains would have had a nigh-impossible time facing Szaeyl, but Mayuri was able to out-think him. Anybody's Bankai but Byakuya's would have been in serious trouble if hit by Zommari's Amor. And, notably, the <5 Espada took multiple Captain-level characters to take down (Nnoitra was Ichigo/Nel/Kenpachi, Ulquiorra was Ichigo/Zangetsu, Harribel was Hitsugaya/2 Lieutenant-level Vizard/Aizen, Barrigan was Soi Fon/Lieutenant/Lieutenant Vizard/Barragan himself, Starrk was 2 Captains/2 Captain Vizard, Yammy doesn't count but still got taken out by 2 captains).

Also notable is the fact that not all of the Espada were Vasto Lorde level - Grimmjow and down were Adjuchas (except #9, who was the only Gillian). And when Hitsugaya first fought Shawlong, they still had the limiter on. Once it was removed he died in one hit.

The reason the Quincy are dangerous is because they have a combination of shared abilities (rarely touched on) and special powers (barely focused on compared to Bankai/Resurrecion). Their powers are also heavily amplified in Soul Society due to the fact that they make use of ambient spirit energy - remember how Uryu was able to fight a Captain when they were trying to rescue Rukia? Except these Quincy have the ability to go all-out without losing their powers, so they more or less have the same potential Uryu had at that time, just on a regular basis. On top of which, they've received a power boost directly from a guy who once went toe-to-toe with Yamamoto.

Power creep is a thing, but the internal logic is largely sound.