LOS ANGELES (Variety.com) - "The Flash" and "Marvel's Agents of SHIELD" have been operating on parallel tracks - not merely adjacent to each other on Tuesday nights, but each building toward and culminating with a "winter finale" that answered questions and resolved plots, while still leaving plenty dangling.

Yet while both shows have their merits - reinforcing this as a "Best of times" for comic-book fans, even on TV, historically a source of wince-inducing corner-cutting and camp - the CW's new DC Comics drama is clearly exhibiting more power, while ABC-Marvel-Disney's sophomore hour has yet to completely escape the feeling that it's spinning its wheels.

In what was almost certainly the best episode of "The Flash" thus far (and SPOILER ALERT, for both shows, if you haven't watched), the series formally introduced the yellow-suited "Reverse Flash" (or Professor Zoom, if you prefer); pitted him in a rollicking fight with the Flash (Grant Gustin); had the Flash's alter ego, Barry Allen, finally profess his love for Iris (Candice Patton); and added one more layer of villainy to the mysterious Professor Wells (Tom Cavanagh).

Even for a show about the fastest man alive, that's covering a lot of ground.

Most impressively, strictly from a logistical standpoint, "The Flash" has continued to provide a healthy dollop of superhero-style special effects throughout the season, without falling victim to the time crunch that has had a way of occasionally turning later episodes of such programs into an Ibsen play. As a consequence, the show has been able to advance its mythology and develop its characters without skimping on action or fun.

By contrast, after an improved start "Agents of SHIELD" is again operating as if it's shackled, in part, by its role as a cog in the larger Marvel universe, which forced the series to play small ball through much of its first season while waiting for "Captain America: The Winter Soldier" to blow up its narrative. Much the same has happened in season two, focusing on locating the mystery city envisioned by Agent Coulson (Clark Gregg) and the shadowy history of Skye (Chloe Bennet), with Kyle MacLachlan having apparently graduated to the Dennis Hopper role in "Blue Velvet" as her wild-eyed father.

While the superheroics have been kept to a minimum this season, there's been a good deal of drama surrounding what Hitchcock would have called a MacGuffin - in this case, a device of unspeakable power (sorry, Indy) known as the Obelisk. There's also been the little matter of that ageless Hydra leader/Nazi (Reed Diamond), who, on Tuesday, met a rather ho-hum and anticlimactic end. Or did he?

Beyond its coy references to better-known Marvel heroes, "Agents of SHIELD" still feels as if the writers must ply their trade with one hand tied behind their backs - asked, as it were, to help set up the fill-in drama "Agent Carter" and tie into the mother ship that is "The Avengers" sequel.

What's left, then, is plenty of impressive stunt work, and less-enthralling banter among the expanded and revised cast of characters, whether that's the squabbling exes played by Adrianne Palicki and Nick Blood; or the sweet but rather tedious unrequited romance, at least in the way it's been teased out, involving Fitz (Iain De Caestecker) and Simmons (Elizabeth Henstridge).

Frankly, with all the synergistic hoops through which "Agents of SHIELD" must jump, the show is probably better than it should be, and Marvel would be doing everyone concerned a favor if it quit worrying about integrating the narrative into its other properties. The movies certainly don't need the help, and "SHIELD" doesn't appear to be benefiting from the relationship, commercially or creatively.

For now, meanwhile, "The Flash" is the one that's blazing a trail -- demonstrating that you really can do a primetime superhero series that wholeheartedly embraces comic-book conventions, and leaving some old perceptions about bringing costumed characters to TV in the dust.