one of lightroom's negatives for me is that i can only use argb space
whereas aperture allows me the freedom to choose. i still use c1 most of the time but i have been trying the other 2 out seriously. lightroom's inability to use other spaces is a big drawback to me...
Actually the approach I recommend is to use ProPhoto RGB in Lightroom, one of the 3 options you have (the two other are sRGB and Adobe RGB). ProPhoto is the largest color space one can export to in Lightroom, thus the safest since the least likely to clip colors.
I also recommend you turn the clipping warnings on after selecting ProPhoto as it will show you if something is clipped in the highlights or shadows or not. You turn this on by clicking on the small icons at the top left of the histogram palette.
In fact you can use the clipping warning with the two other colorspaces provided in Lightroom, sRGB and Adobe SGB, and see if colors are clipped in either of them. Not all photographs have a wide range of colors. In fact, if you try this approach you will be surprised at how many photographs have all their colors fit into Adobe RGB or even sRGB. Just make sure to turn the clipping warnings on and refresh the screen by choosing a different photograph then returning to the one you were working on. Otherwise the software does not always refresh the screen after a color space change.
It is a common misconception that the clipping warning show just overexposed and underexposed areas. The fact is that they also show clipped areas, meaning areas that fall ouside of the chosen colorspace. The warnings work together with the color space chosen as destination for the conversion. They will show different clipped areas when different color spaces are selected. Capture One, and other raw converters, work the same way.
There are two reasons why an area might exhibit a clipping warning:
1-because it is overexposed or underexposed and contains no detail whatsoever. Nothing in this area was recorded by the camera except perhaps image noise.
2-because the color in that area falls outside of the chosen color space. When this is the case, it is usually a single color that is clipped, and not all three. Often, reducing the saturation of that one color will fix the problem.
Once you have exported to ProPhoto you can actually use Holmes Chroma Variants for ProPhoto if you want, since Joseph Holmes has made variants for ProPhoto available last year.
All in all, you lose nothing and have all the advantages of a large colorspace and of the Chroma Variants. Using a large colorspace presents no drawbacks in terms of quality if you stay in 16 bit all the way to the time you send the file to the printer, and if you let the printer do the conversion from the ProPhoto color space to the printer/paper profile color space.