Ah, I guess they just look like they are a bit more secure!
The only mk4 Escort lock I don't like are the early ones that use the jagged key that shreds your pockets! Don't see them very often though!

I'm pretty sure mk4 door locks don't fit, I wouldn't bet my life on it but a while ago I remember I tried to put mk4 locks in my mk3 and the shape of the hole was slightly different IIRC, it was a while ago though..... next time i'm down the scrappy i'll have a look and find out for sure