Only difference will be space and probably price being cheaper to make. Sony always does this.
Online updates will be the same and performance will be identical.
Its not like how the early original fat PS3 had PS2 red laser to be compatible with PS2 games then over the console revisions decided to cut out the PS2 laser and go with emulation instead and that didn't work well with a lot of PS2 games if not at all. Finally the Slim which didn't have any of that leaving the chance for the consumer to maybe find their classic PS2 games online to download if they ever bothered.
PS4 doesn't have anything to resemble the past so all that will be different with the slim revision will be most likely cabinet space and price and maybe larger HDD.