I have to say one of my favourite leopard enclosures in the UK has to be the Amur Leopard Enclosure at Thrigby, in effect it is a Howletts Enclosure with a walkway going through and up to the centre like a stairway to a viewing platform right at the top in the centre.
Lots of climbing oppurtunities for the leopards, and it was quite a nice 'dark' and private atmosphere for them. Very nice, shows not all the best enclosures need millions spent on them with a fancy name.
Linton and Marwell are in comparison very very different, Marwell is now owned by a very large organisation whereas Linton is family owned therefore the way money is spent will be different, bigger enclosures at Linton will take alot more time to plan and build then that at Marwell.
Linton also has 3 species of Leopard, African, Clouded and Snow, all in mediocre but very good enclosures, And a new African Enclosure is in the development stage, at the moment the old leopard enclosure is simply an empty site waiting for redevelopment.