One difference is API e.g. for compressing an array of integers in Java, you say int[] compress(int[] toCompress) i.e. it natively works or Java's int[]. While

One difference is API e.g. for compressing an array of integers in Java, you say int[] compress(int[] toCompress) i.e. it natively works or Java's int[]. While it's true that the layout of data in memory could be re-interpreted as a byte array, you avoid cumbersome casting (which, by itself, might incur cost in languages like Java where you can't just party on memory via pointers). Another difference is that a custom algorithm for compressing integers might gain speed/compression efficiency from exploiting statistical properties of integers e.g. it's a safe bet that in most cases the highest byte of an int is 0 (i.e. integers are are small). Or in many cases a delta encoding is very effective (i.e. {5, 10, 15} => {5, 5, 5} which is easily encoded with run-length encoding). Of course if integers are randomly and uniformly distributed they are just as un-compressible as random, uniform distribution of bytes, but in many real-life uses of integer arrays that is not true.