I use both. I've been on Mastodon for the better part of a year and only actively tried Bluesky the last couple months. My Bluesky feed is thriving, whereas Mastodon not so much. IMO this is due to Mastodon is missing the major quality of life features of Bluesky.

• Add lists
• Subscribable block lists
• Custom subscribable topic feeds
• Optional recommendation engine

These things make Bluesky very easy to get started with and more powerful even than Xitter was. It's simply a better product if you have any requirements other than federation. Getting a good feed up and running doesn't take more than an hour or two. Mastodon is a lot more work.