I recently evaluated both products, so I can speak with some experience.
Octopus Deploy Pros:
- I liked the dashboard, how you see every product, and the current released version on each environment. VSTS just doesn't have this, at least at the account level. Even at the project level you can't easily determine this information. You could look at the latest release, yes, but someone could have redeployed an old release, and VSTS doesn't keep track of what version is on what environment.
- Commercial "Supported" product, if you run into questions about VSTS, there is a community of MvPs here on Stack Overflow, and you can submit support cases with Microsoft, but it's not as straight forward as a dedicated support.
- Documentation: It's absolutely stellar, and all in one place. It's also very well written, with good diagrams/explanations. In my experience with VSTS, documentation is spread out like typical Microsoft, if you have an intriguing question usually you track down a MvP here or through other means, or do lots of searching and figure out something that will work in your case. Unfortunately, the knowledge share for VSTS is just not in place yet, as they've changed their name over the years and keywords you use may simply not rank as high as previous keywords.
VSTS Pros:
- If you already pay for Visual Studio Enterprise Licenses, you get one free release pipeline per license. In our case, our upfront cost is $0
- It's all in one place, and secured with the same VSTS groups. OD required it's own user/group structure
- Cloud based, as opposed to on-premises. This was huge, as you can immediately start using it, and not require infrastructre/setup costs.
- Doesn't require an additional nuget reference/msbuild parameter in your releasable products (OD prefers if you use OctoPack)
Ultimately, we chose to go with VSTS. VSTS has feature parity across most features of Octopus Deploy, they make it incredibly easy to build a solution, create artifacts and release to a variety of environments. The fact it was "free" was a big driver, vs. paying yearly licensing to another third-party product.