Depends on the lldb build. I tested a build that came with fedora, and lldb crashes.
About the speed: If gdb data would be displayed "raw" (without the IDE fixing pascal rules as far as possible), then gdb would be faster too.
Anyway, if you want speed, use LazDebuggerFp (install the package), and choose fpdebug. (Lazarus 1.9)
There are many details, that the gdb based debugger currently has. E.g.
- stepping over an ignored exception (and still stopping after the step)
- stepping out of an exception, into the finally/except handler