There isn't great evidence to suggest that electric toothbrushes are much better at removing plaque than manual. E.g. this metaanalysis [1] found basically no difference.

There are also studies that show that electric is better, like this meta-analysis that found a small effect [2] and this Cochrane review. [3]

What I generally read in articles is that the single biggest thing that makes a difference is brushing for the full 2 minutes, and electric toothbrushes can help with that by having a built-in timer.

1. https://pubmed.ncbi.nlm.nih.gov/38348549/

2. https://pubmed.ncbi.nlm.nih.gov/34877772/

3. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD...