Several key differences between the Apple iPad and the Barnes & Noble Nook HD can sway a purchase decision. Despite superficial similarities in their slate-style form factor, these two tablet computers are entirely different devices. When trying to determine which is right for your needs, there are a few factors to consider.

Operating System

The Nook HD and iPad run entirely different operating systems, giving them very different user experiences. The iPad runs on Apple's iOS, making its user experience comparable to an iPhone or iPod Touch. The Nook HD uses Android with a customized user interface, making its user experience unique to that device.

Screen

The Nook HD and iPad also differ in screen size, pixel density and resolution. The Nook HD features a 9-inch screen, while the iPad features a 9.7-inch screen. Both can display HD video at up to 1080p, but the iPad has a maximum resolution of 2,048 pixels by 1,536 pixels while the Nook HD has a maximum resolution of only 1,920 pixels by 1,280 pixels. The iPad also has slightly higher pixel density, with 264 pixels per inch compared to the Nook HD's 256 pixels per inch.

Processor and Memory

Both the Nook HD and iPad have different processors. The Nook HD has a dedicated Texas Instruments ARM Cortex-9 dual-core processor, which runs at 1.5 GHz. The iPad uses a system-on-a-chip design with the Apple A5X chip, which also makes use of an ARM Cortex-9 dual-core processor. The iPad's processor, however, runs at only 1.0 GHz. The iPad also has nonexpandable hard storage at 16GB, 32GB, 64GB or 128GB depending on the model purchased. The Nook HD has 16GB or 32GB of hard storage depending on the model purchased and is compatible with microSD cards of up to 64GB.

Available Apps

Both devices also have different apps available, based on their operating systems. The Nook HD has full access to the Google Play store, although not all apps available are compatible with its hardware. The iPad has full access to the iTunes store and can run any content labeled as compatible with iPad.

Connectivity

Connectivity is another issue, and varies depending on iPad model. Both the Nook HD and the iPad support Wi-Fi connectivity and Bluetooth wireless. The iPad is available in Wi-Fi only and Wi-Fi plus cellular options. A cellular data plan is required in order to make use of the cellular connection.

Size and Weight

The Nook HD and iPad also have different dimensions from one another. The iPad is 9.5 inches long, 7.31 inches wide and 0.37 inches thick and weighs 1.44 pounds. The Nook HD is 9.46 inches long, 6.41-inches wide and 0.45 inches thick, weighing 1.13 pounds. Cellular-equipped iPads are slightly heavier as a result of the additional equipment.

Cost

The biggest deciding factor will likely be the cost: both Nooks are less than half the cost of the cheapest iPad. The Nook HD comes at two prices: $149 for the 16GB model and $179 for the 32GB model. The iPad comes at eight prices, four for the WiFi-only model and four for the cellular model. Wi-Fi-only iPads are $499 for 16GB, $599 for 32GB, $699 for 64GB and $799 for 128GB. Cellular iPads are $629 for 16GB, $729 for 32GB, $829 for 64GB and $929 for 128GB, as of September 2013.