Personally I find the bigger sensor better. The difference in size between 1/1.7 and 1/1.3 sensors is actually pretty big and biger sensor with fewer megapixels will always deliver better signal to noise ratio, wich means better detail rendering. The pixel count not always can be efficiently converted into real detail and resolution.I hope to see burst mode and underwater remote control in Osmo Action 4 (at least over the basic functions)

So... here are the *differences* between the 3 and the 4

• Sensor size: 3 is 1/1.7" CMOS, 4 is 1/1.3" CMOS
• Depth of waterproof: 3 is 16m, 4 is 18m
• Focus Range: 3 is 0.3m to ∞, 4 is 0.4m to ∞
• Max photo res: 3 is 4000x3000, 4 is 3648x2736
• Still photo: 3 is 12MP, 4 is 10MP
• Video recording modes: all are EXACTLY the same except: 4K(4:3) 3 is 4096x3072 and 4 is 3840x2880

So either these specs were cut and pasted from the Action3 specsheet, or the only real differences are a little larger sensor that results in lower resolution photos and possibly lower resolution video.

Personally, unless the official specs release on Wednesday show something better... I'll wait for the Action3 to go on clearout sale and get one of those...