Use of Irules in persistence profile and vs

There's one thing that I didn't still understand.

 

 

What's the point in having two different irules-based persistence profile types (hash and uie) when the type of persistence is 'de facto' determined by the irule?

 

 

For example , theorically, I can create an hash persistence profile with an irule that use the command persist uie and viceversa.Can I?

 

 

Wouldn't be simplier to have a single "irule" persistence profile leaving the choice to select the behaviour (hash or uie) to the irule? (as it seems to happen anyway...)

 

 

I mean , I have to insert a "persist command" anyway in the irules I associate with the profile...

 

 

Or I didn't grasp something in your explanation?

 

 

Thanks.