Congratulations on deciding to use a laptop tray or stand for using your notebook in bed or on a couch. Even the least ergonomic ones will leave an air space beneath the computer (important for cooling) and will protect you from the heat of the case bottom.
I've used or tested a variety of trays or stands over the years.
For my 15" MPB I've bought a KoolSink aluminum tilt stand. It's a very simple and quite effective design. It protects the finish of my desks and keeps the MBP's case cooler during operation. I like the tilt angle for typing. It works reasonably well for laptop use. And it's convenient for travel, as the MBP will fit inside it and the two together fit into my laptop bag (I slip a sheet of paper between them, to protect the finish of the MBP).
The price, especially combined with a high shipping cost, may seem high for what is really no more than a well-conceived and formed sheet of aluminum. But it is effective.
I also like the iLap. I think the KoolSink is a bit more effective in cooling while the notebook is in desktop use, and the KoolSink is more compact for travel use.
But if I planned to make more use of the MBP in my lap than I normally do, I would have chosen the iLap.
Both the KoolSink and the iLap assist cooling by providing more metal heatsink to absorb and dissipate heat by convection to the air. Both do a good job of leaving air space under the notebook and protecting the user while in laptop use.
I don't see any advantage to using trays with little built-in fans that draw current from the computers battery. Many of them are made of plastic (no heatsink/convection transfer value to speak of) and some are shoddily made.