Every system has pluses and minuses, it just depends what you need and where you live.
OpenHAB, for example, doesn’t have zigbee support. The most comparable to SmartThings in terms of the devices supported is probably Lowe’s Iris, but that does have a $10/month fee. It also doesn’t support custom programming, so if that’s the part you’re interested in it’s not a good match.
As mentioned, the following thread discusses different controller options: