Hero4 Black. Great price right now and does 4k. Highly reliable - but double check the audio when you first get it. Some have a shielding issue that introduces clicking into the audio. Firmware v4 allows for a lot of shutter customizations but you have to manually turn it on when in the gimbal. There are also some sizing problems on the app when you go into record. The previous firmware version turns on and off with the Solo. All of this is covered at length here in the forums.