Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
I'm unaware of major benefit for using a router vs. a L3 switch regarding load balancing or load sharing. I would appreciate learning what you have in mind.
On QoS, routers are definitely much more featured. However, L3 switches do offer some QoS features (some more on Metro switches), and with additional bandwidth with Ethernet handoffs, these QoS features often are sufficient, as they are on many LANs (with similar bandwidths).
In terms of performance, there's no comparison, even though the latest 1900 and 2900 routers are much improved vs. their immediate predecessors. For comparison, a 1941 (and 2901) is RFC 2544 rated at 330 Kpps; the 2951 at 579 Kpps. The 3560-8PC is rated at 2,700 Kpps. When you consider a single 100 Mbps (duplex) FastEthernet link requires 297.6 Kpps, you can easily see how a small WAN router can be overloaded.
Again, though, I'm recommending neither a router or L3 switch, just noting the latter might also be additionally considered when analyzing all requirements, but if a L3 switch is used, I do suggest consider using both a small router and L3 switch to capitalize on the strengths of both devices. (NB: since small L3 switches don't support traditional WAN interfaces, i.e. the current frame-relay, you'll need a device besides it.)
