The Eiffel Tower at Paris Las Vegas is a half-scale replica of the original, 540 feet tall, and its viewing deck sits on the 46th floor. A glass elevator runs up through the middle of the structure to reach it.
The reason to choose this over any other Strip observation point is the position. It stands directly across the boulevard from the Bellagio, so you look straight down onto the fountains. The shows run every fifteen minutes after 8:00 PM, and from the deck you see the whole choreography from above rather than through a crowd at the rail.
The deck is open-air, enclosed in mesh, and staffed by people who will point out landmarks. It runs from noon to midnight daily with last entry at 11:30 PM. Ticket prices vary by time of day and are typically valid for three days from the date booked.