Crossover movie. Despite the name saying vs, they actually team up in order to beat the bad guys of each stories who have also allied together. The plot is nonsensical, and requires retcons in order to work. It's completely written in a way to make the two stories merge together. The dialogue is also pretty wank. With that said, it has the type of action that both series needed.
One of the biggest problem with the 70s Tokusatsu show is their villain of the week format. Despite facing a major villain that's trying to take over the world, said bad guy always sends one of his minion at a time instead of many. Now, there's a couple of reasons for this. One of which being that it would make fight scenes harder to draw and animate, thus taking more time and more money. The other being that they couldn't draw out the series for as long as possible.
This movie rectifies that and gives fans what they had been wanting by having both protagonist take on 10 or so Kaijus at a time, which is pretty cool and fuels the big scale fight scenes that many fans crave. Other than that, it's pretty much like any other episodes of either series, albeit, with better visuals. It's a fun short watch, but that's about it.