Here's what I found:
Following are some of the advantage of IPv6 over IPv4;
1. Larger Address Space: address filed in IPv6 is 128 bits long while the address filed of IPv4 is only 32 bits in length. IPv6 offers very large, i.e.296 address space as compared to IPv4.
2. Better header format: the header of IPv6 has been designed in a way to speed-up the routing process. In header of IPv6 options are separated from the base header. Options are inserted into base header only when required by the upper-layer data.
3. Provision for extension: IPv6 has been designed in a way that a protocol can be extended easily to meet the requirements of emerging technologies or new applications.
4. Resource Allocation support in IPv6: IPv6 provides a mechanism called Flow Label for resource allocation. Flow label enables source to send request for the special handling of a packet. This mechanism is really helpful in real-time audio and video transmission.
5. Security Features: to ensure confidentiality and packet's integrity encryption and authentication options are included in IPv6.
source: blurtit [dot] com/q570064.html