Depends a bit on what you are already using in your setup:
- homematic:
- needs a bridge (ccu) (raspy hw modul and open source software can simulate that bridge)
- longer range than bluetooth / zigbee
- variety of different buttons (2in1, 6in1, …)
- design wise a bit dated
- batteries needed
- reliable (for me)
- Hue / zigbee
- bridge / zigbee usb stick needed
- sleeker design
- shorter range but pluged-in devices mesh enabled (aka pluged-in lights)
- batteries needed
- reliability / compatibility with openHAB: no idea, I’m not using them
- Tradfri (Ikea) - also zigbee
- same as for Hue (Philips)
- the Tradfri binding isn’t properly working since more than half a year…
- Logitech Pop
- never got them to properly work with openHAB
- bluetooth low energy battery less buttons
- @pfink was showing some from EnOcean during the berlin meetup in January
- interesting concept, but as far as I got him:
- low range
- no mesh
- poor openHAB integration
Probably many more 