I found Sumologic to lack features that ELK has such as packetbeats. But you still have to manage the Sumologic forwarding agent and keep under your ingest limit. Additionally my mind never exactly flowed with their query syntax. They refreshed the UI recently and I liked it (aside from compounding my overutlization of tabs haha), you now more easily/graphically select time series from the graph. I can see how it is nice to not have to worry about re-indexing and what type of device the underlying data rests on. I have not tried the ELK hosted solution so some of my criticisms could apply to it as well.