[Vendor jumping in here ... I'm the technical marketing manager at ExtraHop.]
From a price-per-device standpoint, ExtraHop is going to beat the heck out of CA Spectrum. However, it's a bit of an apples-to-oranges comparison because the two products are doing different things. Concerning ecosystem, we can send alerts or events to managers-of-managers through rsyslog and SNMP traps.
Where it sounds like ExtraHop could really help is with the POS scenario you described. For one thing, we scale much better than Coradiant (sustained 10Gbps) and offer custom-defined transaction analysis that does a great job of giving you just the data that you need to look at. We can inspect the HTTP payload to extract transactions matching a specific account ID, for example. This demo given at Splunklive shows how easy it is to run this type of customized analysis and answer questions. The demo part starts at 14:00:
ExtraHop also recently introduced precision packet capture that enables IT teams to set policy on automatic packet captures. What's really cool about this is that it not only triggers the packet capture, but pulls the packets from the buffer that preceded and caused the event. So you could see what request caused an application error, for instance. Here's a four-minute demo of the precision packet capture functionality: