A great place to start is seeing the differences between the switches is here http://www.cedmagazine.com/article.aspx?id=68830
Then there is an article on how layer 3 improves latency here:
And lastly a feature list of what your layer 3 router should have:
<ul>Multiprotocol support. IP switching and routing isn’t the only function that Layer 3 switches perform. New models can also handle protocols such as Novell IPX, AppleTalk, XNS and IBM SNA.
Peer router support. Because Layer 3 switches support current routing protocols, they should participate as peers of software-based routers in IP or other networks.
Multicast control. This is the ability to broadcast multimedia traffic such as streaming video.
Management support. Simple Network Management Protocols let diverse network gear communicate. The various levels of advanced RMON, or remote monitoring, protocols give network managers the ability to manage their Layer 3 switches remotely from a central console along with other network equipment.
Spanning tree support. The industry-standard Institute of Electrical and Electronics Engineers 802.1D spanning tree protocol protects against network loops and provides redundant network paths.
Port trunking. Port trunking sets backbone links by treating multiple parallel links as a one backbone pipe. Network redundancy is thus provided, as traffic on any failed link automatically switches to other links.
VLAN support. Virtual LANs allow PCs, servers and other network resources to be organized into logical domains so that only devices within the same domain can communicate with each other. The IEEE 802.1Q standard enables switches to automatically learn VLAN configurations.
Flow control. Flow control is a feature that eliminates dropped packets on congested ports. The IEEE 802.3x standard supports flow control in full-duplex situations.
Layer 4 support. The newest category of Layer 3 switches includes support for Layers 4 and above of the Open Systems Interconnection model. This ensures a full measure of traffic control and contributes to the ability of the switches to provide advanced quality-of-service support.
Fault tolerance. This may include dual CPUs in some cases, but it may also mean dual or backup power supplies and redundant cooling fans.
Hot-swappable. Interface modules holding various port configurations and other components may be swapped without shutting down the switch. </ul>