To begin with, Cowboy Bebop's animation and audio quality are constantly greater than Trigun's (that is not to say Trigun is bad in that regard by any metric, CB is just amazing-er). This is primarily due to the production's budget and the talent of the people involved. The director of Cowboy Bebop, Masaaki Yuasa, also did the screenplay for Trigun so they're not completely unconnected stories. Finally, Trigun has more action and less drama than CB, although both shows deal with similar subjects (e.g. crime and its effects on the characters).
Trigun has a lot of similarities with Cowboy Bebop in terms of story and setting. Both shows are set in the near future where technology has gone backwards (some might even say it's become medieval). Gunmen use motorcycles as their primary mode of transportation because cars don't work anymore (or maybe they always worked but no one wanted to be killed by their vehicles). These gunmen fight crime using superpowerful guns that can destroy cities. In addition, the main characters of both shows go by the name of "cowboy" or "vigilante". The only difference is that while Bebop is based in New York City, Trigun takes place in a fictional world called the "Verdant Green", which sounds like another name for Japan.
Now, despite these connections, Trigun is a separate entity from Cowboy Bebop.
Even now, the animation quality throughout the film is excellent. While there are clearly more spectacular examples of amazing accomplishments in animation, Cowboy Bebop does not disappoint and gives off a nostalgic vibe with its now vintage art style and overall aesthetic. The characters are also very likeable with their unique personalities and tones of voice.
The story follows a group of people after they meet on a lonely road in the middle of nowhere. Each one has a mysterious past that connects them together and forces them to work as a team to escape from their problems and find a way home.
It's an exciting adventure filled with crime scenes, deadly battles, and even some love stories along the way! If you're a fan of science fiction or anime, then you'll definitely want to check out this film when it comes out later this year.
Trigun is similar to Cowboy Bebop in many aspects, but it differs in that it expands on the Western concept, having the iconic cowboy style and bounty hunters in the shape of two insurance agents who are hard on the main character's tail. Also, unlike Cowboy Bebop which takes place in a futuristic city, Trigun is set in a fictional version of 20th century America where magic and aliens exist. Finally, Trigun has more of an action/adventure theme to it than a drama series.
Here are some other anime that are also set in the future but not from the same time period as Cowboy Bebop: Kill Bill, Ghost in the Shell, District 9. And here are some other anime that are set in the past but not from the same time period as Trigun: Brave New World, Planet of the Apes.
So basically, Trigun is a mix between a Western and a futuristic anime with elements of action, fantasy, and science fiction.
I would say it is one of the best anime of all time.