Both versions of The Flash applied the use of nanotechnology relatively much later in their superhero careers.
For Gustin, the first we saw his character's use of nanotechnology was in The Flash Season 7 premiere; upon the speedster waking up from his much needed rejuvinating & rechargable nap, in hopes of defeating Mirror Monarch.
Miller's Flash on the other hand, showcased his character first using the technology in his titular-titled film, for his new, and technollogicaly-advanced suit, which was a gift from Bruce Wayne.
Of course, The Flash-film had a budget 100-times more expensive than a single Flash episode which airs on The CW, so for most people, the quality of the nanotechnology would be in the films favor.
The film also succeeds in the nanotechnology-cowl interfering with an environment i.e., Ezra Miller's hair, which we see strands of being moved upon his cowl retracting in his suit, while Gustin's hair remains untouched, as if nothing was ever concealing his head in the first place.
There are many other nit-picky differences between the two, but that is ultimately up for you as the fans to decide.
Whose nanotechnology do you prefer more?
Worlds collide when the Flash uses his superpowers to travel back in time to change the events of the past. However, when his attempt to save his family inadvertently alters the future, he becomes trapped in a reality in which General Zod has returned, threatening annihilation. With no other superheroes to turn to, the Flash looks to coax a very different Batman out of retirement and rescue an imprisoned Kryptonian -- albeit not the one he's looking for.
The Flash is a 2023 American superhero film based on the DC Comics character of the same name. Produced by DC Studios, Double Dream, and The Disco Factory, and distributed by Warner Bros. Pictures, it is the 13th installment in the DC Extended Universe (DCEU). The film was directed by Andy Muschietti from a screenplay by Christina Hodson, based on a story by Joby Harold and the writing team of John Francis Daley and Jonathan Goldstein.
It stars Ezra Miller as Barry Allen / The Flash alongside Sasha Calle, Michael Shannon, Ron Livingston, Maribel Verdú, Kiersey Clemons, Antje Traue, and Michael Keaton. In the film, Barry travels back in time to prevent his mother's death, which brings unintended consequences.