It’s hard to say if WordPress is the best for SEO without extensively testing all platforms claiming the same, using the same goals, and on the same conditions.
No one has done a real-world test drive ranking competing for websites on multiple platforms for the exact keywords and sharing the results.
Anyone saying otherwise is just click-baiting you :)
A better question, on the other hand, would be:
Will using WordPress help with SEO?
The answer to that specific question will be a solid “yes, it will.”
WordPress will give you more control and help you better and quickly implement a couple of on-page SEO-related features that require extensive/expensive work if done on other platforms.
Here is a couple of them:
- Having a fast-loading page (requires picking the right theme and optimizing/caching it properly)
- Using features-rich SEO tools
- Using rich snippets on the appropriate content
- Controlling social sharing output
A couple of things to consider when switching to WordPress from another platform
When you have a ranking website on another platform, switching to WordPress can be tricky and risky if not handled properly.
Attention to detail is vital.
For example, you pick the wrong permalink while omitting redirects and risk losing it all.
That kind of focus and attention doesn’t usually come like Fiverr cheap :)
The more pages you have, the more demanding the task will be to make sure to keep at least the ranking intact.
Will you see actual improvement if you make the switch?
It depends on your current state and how the competition is ranking.
I would say there will be an improvement if everything is done correctly. As I said, WordPress has the tools to help with SEO. But using them correctly is up to the service provider’s capabilities.
Will it be enough to top your competition?
Making abstraction to the content and backlinks, WordPress will give enough control and tool to help enhance all remaining ranking factors that can be controlled on the website-side.