Choosing between BSD/ISC/MIT is essentially just choosing which phrasing you like best; the basic idea is the same. Almost all arguments in favour or against the 2-clause BSD license also apply to the ISC license, and vice versa.
Under the BSD license, what requirements exist for redistributions that are neither source nor binary in the regular meaning of those terms?
Presumably there ought to be one, but... the license doesn't say.
What about redistribution of the product of macros/meta programming? Redistribution of the assembler output?
Thought experiment: I publish a library in which the .c file is released as public domain but the .h file (which has no function definitions, `static` or otherwise, and had no function-like macros) is released as BSD-2.
The header file will essentially disappear during compilation. You cannot make a .o out of such a header; there is no binary format of it.
Is the resulting binary covered by the BSD license?