The ideal room size for a 40 inch LED TV will depend on various factors such as the viewing distance, the layout of the room, and personal preferences. However, as a general rule of thumb, a room size of around 120-150 square feet is suitable for a 40 inch TV.
As for the brand, there are several reputable brands in the market that offer high-quality 40 inch LED TVs. Some of the top brands to consider include Samsung, LG, Power Guard, Sony, TCL, and Vizio. It's important to do your research and compare the features, picture quality, and pricing of different models before making a purchase decision.