Evo and Pro differences and large size SSD question please

[AssaTM]

Hi all, im wondering what the differences between the 840 pro and the EVO Samsung SSD's are please? and I remember someone mentioning before (could have been totally wrong) that higher sized SSD's are a little slower or get slower faster? is that still true? or was they talking out of thin air? as I think the 500gb EVO is fantastic value for money, thank you for your help

 

[AssaTM]

yeh thats what I was wondering if i'd really be able to tell the difference

Edit: I read that the EVO has a cache like system so the performance isnt always the same, is this noticable or not really at all? I only read it at a glance today so im really uninformed on how the cache system in the EVO works, or if it's even noticeable at all to be honest