It is all about features, and the quality of the device.
You can usually check the quality of the device by looking for reviews for that particular device.
Features you want to look at
- Port count, and link speed for each port
- Remote administration features. How will you configure the switch, http, https, ssh, telnet, proprietary tool.
- The bandwidth of the backplane. A switch should be able allow for lots of simultaneous conversations. For a 1GB, you might expect to see a 10GB backplane.
- VLAN support, this allows you to have multiple virtual networks.
- Etherchannel/Bonding/Link Aggregation. It is possible to merge many ports into a single trunk.
- Routing/Firewalling L3 features. These days, many advanced switches including routing functionality.
- Quality of Service (QoS), if you will be using Voip, having QoS is pretty much required.
- Stackability, Many switches can be stacked using a special cable which allows them to be managed as a single unit.
- POE, some types of devices like phones can be powered by a switch.
If you have a small network, you probably don’t really need most of the features, and a simple inexpensive switch will be fine. If you have high security demands, a VoiP system, a complex network, you’ll need more features.