D5500 model - two questions

[gayleard]

I bought an UED5520 Samsung Smart TV in Dublin at Christmas.
I like it very much, though I haven't explored it much,
as I am on holiday in Italy.
I'm thinking of buying a similar model here (in Italy),
but have two small queries:

1. I only see the D5500 here.
Is there any real difference between this and the D5520?

2. I see advice on this forum to get a D6*** TV rather than D5***.
But I'm not interested in 3D TV, which I thought was the main difference.
Is there any other advantage in the D6000 series?
I should say that I am very interested in computer-related use of the TV,
in particular use with IPTV.
(I've added the TV in Dublin to my local network,
but haven't explored the possibilities.)

Any advice or suggestions gratefully received.