You are comparing systems that generated completion text based on statistics and correlation with a system that now models actual complex functional relationships between millions of concepts, not just series of letters or words.
The difference is staggering.
It comes about because of the insane level of computational iterations (that are not required for normal statistical completion) mapping vast numbers of terabytes of data into a set of parameters constrained to work together in a way (layers of alternating linear combinations followed by non-linear compressions) that requires functional relationships to be learned in order to compress the information enough to work.
It is a profound difference both in methodology and results.