Layer 3 switch doesn't provide the typical edge features used on a router:
- NAT/PAT (along with IPv4->IPv6 transition technologies)
- Stateful Firewall
- HQoS for multiple classes of traffic at a rate Ethernet is shaped/policed on the ISP side (usually you'll get subrate service, not full bandwidth of the Ethernet port connected to the device)
That said, for the inter-vlan routing in most of the scenarios the L3 switch will perform better and cause less problems, as small/edge routers are still using CPU to route the traffic and performance may be not ideal.
So propably you'll want L3 switch and edge router.