What’s the tradeoff?
The shiki integration only handles syntax highlighting, while lezer does a lot more than just syntax highlighting, lezer is the foundation of many intellisense features. And also lezer is super performant with its incremental parsing, and its parser system is interruptible and resumable, so it won’t freeze the UI.
Does this convert to lezer?
No.
From my experience, I usually use this integration for syntax highlighting, and combines with @codemirror/lang-* packages or language service to provide intellisense features.