The main benefit of VLANs are flexibility, you're no longer restricted to one subnet per switch. This can have real benefits when replacing switches with larger models, as it allows you to have more than one subnet on a single switch, which saves both hardware and time required to renumber everything to a single subnet. In the case of our datacenter switch, we have six subnets on that thing (a Cisco 6509), and we were able to add a 7th (a firewall DMZ) with only some changes to the Cisco IOS config file in the switch.
The main benefit of VLANs are flexibility, you're no longer restricted to one subnet per switch. This can have real benefits when replacing switches with larger models, as it allows you to have more than one subnet on a single switch, which saves both hardware and time required to renumber everything to a single subnet. In the case of our datacenter switch, we have six subnets on that thing (a Cisco 6509), and we were able to add a 7th (a firewall DMZ) with only some changes to the Cisco IOS config file in the switch.