On the other hand, if it's available, Valgrind will do a better job of catching uninitialized memory use if you use malloc instead of calloc.

(IMO, explicit initialization is better than just zeroing stuff out, because there's no guarantee that zeroed memory is valid. Especially when pointers are involved—dereferencing a null pointer in C is undefined behavior, so compilers are free to wreak havoc on any code that it can prove attempts to do that...)