This double feature comprises of Gunbuster and Die Buster (aka Gunbuster 2) condensed them into a single theatrical release told in two parts with a musical intermission in between. The first part, Gunbuster the Movie, condenses the six episodes of the original OVA into a 95-minute movie featuring a new 5.1 audio remix and a redub by the original Japanese cast. The second part, Die Buster the Movie, mixes large chunks of the second OVA series with a few altered or newly-animated scenes to create a truncated take on Nono's story.
Recommendation: Watch the original series instead. This is basically a long summary with nothing new whatsoever, so only come here if you're looking for a quicker rewatch.
Starting out, I wondered if I could get away with simply watching these movies instead of the series considering that they both reflected the same story. I knew the series would have more material, but maybe these newer movies might have updated visuals, or might tell the story better or at least more succinctly? Unfortunately, no: I'm pretty sure the movies have no new scenes, the visuals are the same, and the plot moves past succinct
Both series are condensed enough, but these movies condense past the point of comfort. With all the cutting they had to do, scenes jump around a bit more than they should. The brunt of the action's there, but the development to that action, and especially the reasoning for that action suffers in the movies.
But please do try the original series! They already have excellent reviews on MAL, so I won't unnecessarily delve into them here. But I'll just say this: if you don't like Gunbuster (Top wo Nerae), please still give the significantly more modern sequel a chance (but do know that although the stories and characters of the two OVAs are mostly separate, you'll enjoy Diebuster (Top wo Nerae 2) more having first finished its predecessor. It's a spoiler to say why). Dazzling protagonists that evolve well throughout each episode... rare beasts indeed, but we find one in both. Come back for these compilation movies only if you get the urge to rewatch both of these underground gems.
Gunbuster and Diebuster: Two titles that represent different turning points in Gainax's history and serve as the precursors to their more renowned works, Neon Genesis Evangelion and Gurren Lagann. Does the appeal of these OVAs extend beyond their legacy? Let's find out.