What continuous deployment software would you recommend? What does your top pick offer that other vendors don’t?

Your organisational needs and context matter hugely as well as your existing and target tech stack….

Are you looking to implement modern deployment and release mechanisms (blue/green, canary etc)?
What are the target application hosting environments, on prem, windows, linux, containerised, virtualised, bare-metal, cloud native, AWS, Azure, GCP, specialised hardware ?
How do you intend to integrate with your change management system of choice e.g., ServiceNow ?
What automated guardrails and policies do you want to put in place to assure security and quality ?
Do you work in a regulated environment and what standards do you need to meet and retain evidence of compliance ?
What are your CI systems of choice ?
What other systems and processes do you need your CD solution to integrate with ?
Are you comfortable expressing your CD pipelines as code or do you prefer a more visual approach ?
Do you want or need human beings to make deployment approval decision either as standard or by exception ?

There are some great tools available offering fantastic CD capabilities that help address questions like the above - if you can explain a little more about what you are trying to achieve and your particular context then I (and others) would be happy to make suggestions on CD technologies.

For continuous deployment (CD), my top recommendation would be GitLab CI/CD for its all-in-one platform, which brings together version control, CI/CD pipelines, and a wide range of DevOps tools. Every tool comes with its merits and demerits. For instance, GitLab offers a unified DevOps experience with fewer external dependencies compared  to Jenkins which requires heavy customization and plugin management, which adds maintenance overhead. Bamboo is well-suited for teams using the Atlassian suite but has fewer cloud-native features.

If the goal is to streamline DevOps workflows and reduce tool overhead, GitLab CI/CD generally offers a more integrated, out-of-the-box experience that can improve efficiency and team collaboration.

Often, this should be influenced by your technology stack.

If you're using github, then github actions can be a great choice for build/deploy automation.
If you're deploying to AWS and your team is well versed in AWS, there are CodeBuild, CodeDeploy.

AzureDevOps has it's own system.

If you're looking for something like Jenkins, Octopus, etc...  it would still come down to your teams deployment needs and familiarity.  The best or most complex tooling might only serve to cause issues and trouble if your team can't support it.

I've used all the above, and found that if you take the time to learn them, there are few use cases that they can't support.