There are varying degree of sex-crimes in the dystopia of 1984. Winston's consulting with the prostitute in Part I chapter 6 is not as risky as meeting secretly with Julia in the woods.
Consorting with prostitutes was forbidden, of course, but it was one of those rules that you could occasionally nerve yourself to break. It was dangerous, but it was not a life-and-death matter. To be caught with a prostitute might mean five years in a forced-labour camp: not more, if you had committed no other offence.
The prostitute is a Prole and not so much of a threat as Julia, an Outer Party member and organizer in the Junior Anti-sex League.
In terms of Chiaroscuro (contrast of light/dark), the encounter with the prostitute is set in a slum which is dark and dank. Winston is afraid to turn on the lights. When he does, he discovers nightmarishly that the prostitute is less than he expected:
When I saw her in the light she was quite an old woman, fifty years old at least. But I went ahead and did it just the same.
In the Golden Country, or The Place Where There is No Darkness, Winston and Julia meet in a Garden of Eden setting. There are no cameras, no bombs, no Secret Police. It is an idyllic setting.
As well, Julia is young and lithe, not a wrinkled hag. There is no Oedipal guilt when Winston lies with her. The natural light on Julia symbolizes a freedom Winston has never experienced. The woods, though dark shelter, offer a welcoming surrounding devoid of technology and fear.