That's only an scalar code optimization though. You can still do comparison in constant time on little endian data, you just lack the ability to early-exit from the loop. In the modern world of SIMD data, that optimization often doesn't exist. Fair enough point though.

But comparison is done in registers which don't have a byte order. Unless you mean doing something like 256bit_a > 256bit_b which I would think it's a very rare operation. Good point though.

To follow up on this, I recently implemented a packed vector format. As a LE advocate I surprised myself by ordering the packing in BE order — because that let me simply byte-compare vector encodings to compare the underlying vectors, which was a huge performance increase.

Data structures which are frequently compared, e.g. to be sorted, benefit from BE ordering. Just binary compare them as byte strings, usually an efficient inline operation.

If I were implementing a packed wire format for SQL data, for example, I’d probably do it in BE order.

In the worst case, comparison is still like subtraction.

Even if the whole datum is examined, comparison is more parallelizable; it doesn't require carry propagation.