@Kiran,
As far as I know, 7.1.2 reached the End-of-Support cycle. You have no choice but to upgrade 
I suggest you to upgrade to 9.6, as it has better features of command central, cloudstream, MFT, elastic ESB, etc. More at: The Web page cannot be found
Regarding advantage/disadvantage we need to understand your requirement. If I get you question correctly, you want to know what challenges you face during 7.1.2 to 9.X migration.
Please clarify.
Thanks,
Rankesh
#webMethods#B2B-Integration#Integration-Server-and-ESB