I can't comment on the Lefthand or cross-site functionality of either. What I can say is that I managed a 100TB EMC Unified shop and the 30TB Equalogic we used for iSCSI was 100x more reliable and easier to work with. Ultimately, we used the Equalogic whenever we had the opportunity, and the EMC's sat there doing nothing.
Equalogic is a solid SMB platform.
With the lefthand there are 2 types of protection going on. The first is the Raid level inside a single node (this is standard raid accross the disks in that node, usually Raid1 or Raid5)
When you add a second node on the same site, you can setup network raid. this mirrors a lun to both nodes, so if a Node fails, the lun can continue to be presented to the servers.
when you add the remote site nodes into the network raid, that lun is also mirrored to the remote site nodes, so you effectively end up with 4 copies of the data.
For the EQL box, whilst there is only 1 node each site, those node are more resilient at the hardware level. the disks in the node will be raided, and their are 2 physical controllers in each node. If a controller fails the node will switch to the other one.
If you add a second node on the local site with EqualLogic, and add it to the Group all luns are stripped between the 2 nodes, increasing performance.