Communication features are key in any handheld. How does the device communicate via wired ports? That’s mostly via USB today, but USB may be via a special docking port, a proprietary cable, or via various types of USB ports. There are over half a dozen different types of USB connectors. The specs should tell you exactly what’s available. If legacy serial connectivity is available, what port does that use? Or does it need a special adapter cable?

Moving on to wireless connectivity, the specs should state exactly what type of WiFi, Bluetooth, and mobile broadband (WWAN) the device supports. With WiFi and Bluetooth that’s relatively straightforward, but WWAN comes in numerous generations, frequencies, bands, and technologies. The specs should be very specific here. If GPS is required, the specs should provide an indication of approximate accuracy, whether there is A-GPS (assisted GPS that shortens start-up), and which of the international positioning satellite systems (i.e. GPS, GLONASS, Galileo, Beidou, etc.) are supported.
There are different ways of data capture, so specs should be precise in what is available. Barcode reading can be simply via integrated camera, or via dedicated scanner modules. The latter may be able to read just linear barcodes or 2-dimensional codes, and they may use LEDs or actual lasers. NFC and RFID readers, likewise, come in numerous versions. The specs should include the basics and list the exact type of module so customers can google its detailed specs.
Sensors are becoming ever more important in handhelds, and the specs should tell which are included in a device.
Cameras have become ubiquitous in handheld computers. Specs should at least show basics for both stills and video, as well as what software controls the camera(s).

It’s often difficult to figure out from pictures how large a handheld device is. Examine at the specs and use your smartphone as a point of reference to get an idea how large the device is.