"1) What's the difference between WS-C4948-S and WS-C4948-E? "
I believe that denotes the level of the installed IOS feature set (-S, -E):
"The IP Base feature set includes advanced QoS, security, and basic routing functionality.
The IP Services feature set provides a richer set of enterprise-class features, including advanced hardware-based IP unicast and multicast routing as well as Virtual Route Forwarding (VRF), and policy-based routing (PBR). "
"2) The 3750-E does hardware-based mulicast routing. is this the same for the 4948's? "
I don't know for sure, but very likely.
The biggest obvious difference between the two, the 3750-E can be stacked, the 4948 can not (likewise the 3560-E can not). Also, the 3750-E comes with two 10 gig module ports, the 4948 can be obtained with or without 10 gig module ports.
The 4948, I believe, is really a 4500 sup without the chassis. It seems to runs the same software as other 4500s. I'm sure there are some subtle feature differences between the two switch series (4848 vs. 3750-E).
For raw performance, both seem to have very similar specs for a single device (also the 3560-E). The 3750-E's performance can be impacted by stacking them where the stack offers less bandwidth then a single switch's fabric (although more than a Ethernet port, including 10 gig).
With regard to the impact of multicast, much I would think would further depend on the number of sources and number of receivers. I would think a single source, even if all ports in a maximum stack were receivers, would likely be okay for the bandwidth you've noted. Again, though, not positive.
You didn't mention how many ports you need or what other load the switch needs to support. If a single device offers sufficient ports, and you don't need 10 gig, the 4948 or perhaps even a 3560G would be best choice. If you need 10 gig, then the 4948-10GE or 3650-E would be best choice. If you need more ports than one device can offer, and the switches are not at a distance, then the stackable 3750-E or even the 3750G might be best choice.
I've mentioned the 3560G and 3560-E, both are about identical to their 3750 counterparts except they can't be stacked.
I've also mentioned 3560G and 3750G, both can provide wirespeed for up to about 24 gig ports. If you won't be fully loading more ports, they too might serve with regard to speed and latency.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...