KL Tower - Sky Deck and Skybox are on the same level, Level 5, open air, the highest level permitted to visitors. Having paid extra for access to Skybox, which turned out to be only 45 seconds per person, I was unimpressed by it only having 2 panels of floor glass to see the full drop view. Visitors ticket numbers constantly being called for Skybox over the loudspeaker is very annoying, and loud, and ruins a certain atmosphere that should be felt while blooking from such a height over KL city.
Observation Deck, Level 4, gives a far better view with it's angled outward windows, unobscured by the concrete outer ring that is on Sky Deck Level 5.
Observation Deck, Level 1, has bars in front of the windows restrict leaning forward for a better view.
Overall we had a good experience as we were there early evening with enough daylight to see across the city, but also stayed long enough for daylight to fade and to see buildings across the city light up