The advantages of the HO scale for model trains include small size, wide variety with detail, reasonable price, large-scale support, variety of available trains and accessories, and availability. These combine to make it a popular scale for older children and adult hobbyists.
The wide turning radius of the HO scale is a difficulty with layout at times. Also, manipulating the HO scale is hard for children who are younger than 7 years old. The track pieces and trains are fragile, and the availability of operating accessories is limited. Finally, the DC wiring with the HO scale is unusual, making rearrangement tricky.
Users wanting to create a simple layout need a space that is at least 4 feet by 6 feet because of the turning radius of the track. The reasonable cost of HO track and cars -- about $40 for a train set, as opposed to a cost of about $150 for O scale, as of 2015 -- makes it attractive for new hobbyists. HO tracks and accessories are often the cheapest, as freight cars can be as cheap as $4, and locomotives are available for less than $20. With O scale, the starting price for a locomotive is at least $50, while the average price is about $100.