Best CT connected energy meter rating for a CT with secondary 5A

I work in a Maldivian Utility Company. Our engineering team is pretty weak so I don't have anybody in the company to ask even though this is the state electric company.
A supplier quoted us 2 CT meters . Rating for one is given as 1A(6A) and other as 5A(20A) which I believe is 1A basic current Ib and 6A Max current and in other case 5A basic current Ib and 20A Max current.
Supplier is recommending 5A(20A) saying that 5A Ib meters is the standard approach for the 5A CTs and 1A Ib is for CTs with 1A secondary current.
But my understanding is 1A(6A) meters fit better with current range of 5A CTs.
I would like to clarify what is the standard rating for 5A CTs and point me to is any literature to get more information about matching meter rating with CT secondary rating.
Sorry for the bad English.