colour has lower inherent resolution than mono, but the difference can be minimised with efficient processing.
http://www.stark-labs.com/craig/reso...yering_API.pdf
Asimov was a regular contributor here and was able to produce very high quality images with a colour sensor. If you are intending to get heavily into planetary imaging, go mono for the extra few percent, but otherwise, it seems to me that colour is a viable alternative. The other way to look at it is that a colour camera is now cheap enough that it is no longer such a big deal to write off 30% by selling it used, if you later decide that you want to go mono.
Are the ZWOs and QHYs so good that there is no need to consider anything else anymore?.. on balance, probably yes at the moment. Looks to me like the MT9M034 (ASI120, QHY5L2) is right at the cutting edge with 75% QE and low noise - from limited reading I can't see anything (affordable) to beat it on the horizon. Remarkable that it is also really low cost. The MT9M034 has most of the camera on-chip, so it seems likely that any other makes of camera using this chip will have similar specs. It might also be worth a look at the PointGrey Grasshopper3 with the Sony imx174. It has similar QE to the ASI120 but uses USB3 to support very high framerates at full frame - but it costs 4x? as much and the large pixel count would not provide much advantage over the ASI120/QHY5 for planetary imaging (great for lunar or solar though).