There are three types of tire-pressure gauges: stick, digital, and dial. Stick-type gauges, which somewhat resemble a ballpoint pen, are simple, compact, and affordable, but they are a little harder to read than most digital gauges.
Digital gauges have an electronic LCD display, like a pocket calculator, making them easier to read. They're also more resistant to damage from dust and dirt. Some digital readouts light up, making them handy for checking pressure in low-light conditions. On the down side, however, digital gauges are a little bulkier than stick gauges and they require batteries. While batteries can last for years, depending on use, they will run down eventually and need replacement.
Dial gauges have an analog dial, resembling a clock face, with a simple needle to indicate the pressure. Some dial gauges have more features than pocket-sized gauges--including an extension hose, bleeder valve, dual-scale dial, and shock-resistant dial cover--but we have found that they aren't necessarily more accurate. Most dial gauges are easy to read, but models with an extension hose take two hands to operate. They can also be bulky and typically cost more money, running from $20 to $50.
Buy a gauge with a wide-enough range that it can measure the pressure in a temporary spare, which is typically 60 psi. Many gauges have a span of 5 to 99 psi.
If you need to check pressure in a darkened area, consider a digital gauge with an illuminated display.
If you buy online to save money, check shipping charges to see if the purchase is still a bargain.