Incapacity benefit while in receipt of Pension Credit

Hi there

I saw a client this morning who is receiving PC & incapacity benefit and has received an ESA50 to migrate over to ESA.  I checked with the Pension Service and Incapacity Benefit as to why he is having to go through the migration when he has been in receipt of PC for nearly 2 years.  I was advised that he could close his incapacity claim - it was up to him and that there was no advantage in remaining on incapacity. 

Is there any benefit in the client staying on incapacity/migrating over?  He does not want to endure an Atos assessment due to severe learning difficulties (on HRC DLA indef).

Many thanks

I have seen a previous post - it mentions deprivation of income.  Should my client just not return his ESA50?