Is this an issue?

[DSMan195276]

Maybe instead of using a DLL to add functionality, let's look at what it is you ultimately want the DLL to do. Is it something that can be done directly in QB64, avoiding the overhead you would incur by using an external library?

Well the reality here is that the 'overhead' of using an external library is basically non-existent, and with that a C version of some functionality will basically always be faster than a QB64 version. But I don't think this should be all that surprising, lots of languages are like this. The advantage of a language like QB64 is ease of use, not speed at all costs.