tcp/ip 6 accounts for extremely little efficiency - almost zero
MOST CONSUMER SPEED PAID FOR IS ACCOUNTED FOR BY TONS OF EQUIPMENT, WHICH INTEL CORPORATION. WHEN YOU PAY FOR 2 MB, 1.9999 OF IT IS DELIVERED BY INTEL, NOT TCP/IP 6 "improvements" over tcp/ip 4
(that google continually attacks to attempt a\ chinese network gear over-throw of intel, #ARM, #tcp6)
lastly, tcp/ip 4 was and is unlimited. it had empty slots to allow extension (which tcp/ip 6 developers deceived the public about), tcp/ip 4 can have __anything__ in it's payload - so the idea it could not carry features - just purely lies