That is a deep and interesting question. I'm not sure I can give a great answer, but here are a few thoughts. If we look at the file format itself (separate f

That is a deep and interesting question. I'm not sure I can give a great answer, but here are a few thoughts. If we look at the file format itself (separate from the features/semantics of the linker and loader), I think ELF is simpler and more orthogonal. You can iterate over the section/segment tables of an ELF file without knowing anything about what each section/segment means. ELF nicely decouples the high-level "container" aspect of the file format from the lower-level semantics of how you interpret each section/segment in the linker and loader. Mach on the other hand couples these two concepts together. The top-level table is an array of "load commands", each with its own type, but you can't even parse a load command until you know what type it is. Unlike ELF, the entries of this table do not have a generic format or even a consistent size. If you haven't written code to specifically recognize a given command type, all you can do as fallback behavior is skip it. To me ELF feels like a refactoring of Mach to make it a little more general and layered. If we consider the actual semantics and features of the file formats, there are pros and cons to both. Mach-O has built-in support for fat (multi-architecture) binaries, which is kind of nifty, though I've never actually used it myself. Mach-O distinguishes between "dylib" and "bundle" for shared libraries -- for the life of me I can never remember the difference between these two -- whereas ELF just has one type of shared library. (https://docstore.mik.ua/orelly/unix3/mac/ch05_03.htm https://docstore.mik.ua/orelly/unix3/mac/ch05_03.htm). The distinction seems to add complexity and I'm not sure I understand the benefit. Mach-O has two-level namespaces (dynamic symbols are resolved by both name and the library they come from) -- colliding symbols aren't generally a problem I've seen with ELF, but maybe it's useful in some cases. ELF makes symbol interpositioning easy with LD_PRELOAD, though Mach-O seems to have its own version of this that I've never tried: https://stackoverflow.com/questions/12609728/changing-function-reference-in-mach-o-binary https://stackoverflow.com/questions/12609728/changing-functi.... Overall I prefer ELF.