The dll generated by MATLAB Coder is able to run without MATLAB Runtime, so it is deployable in such as embedded hardware which don't have much spec as PC nor servers. But MATLAB functions which can be converted to dll by MATLAB Coder are limited.
In the other hand, dll generated by libraryCompiler (a tool of MATLAB Compiler SDK) needs MATLAB Runtime (for free) in order to run. MATLAB Runtime requiresthe same machine specs as MATLAB, so the dll would only work on PCs and servers, not on embedded systems.
For detail of comparison between MATLAB Coder and MATLAB Compiler SDK, please seethis answer.