You have a slightly wrong understanding of color spaces. Let me help you here...
- both sRGB and aRGB are 8-bit-per-color spaces, both only support 16.7 Million colors
...it is like 1000-value numerical system: I can count 1000 values by 1's from 0-999 or I can count 1000 values by 2's from 0 thru 1998 ...but only 1000 values with either system!
- If you work with RAW data in a program like Photoshop or Lightroom, they work internally in a 16-bit-per-color space, and only 'convert' to sRGB or aRGB when you choose to export a JPG output file
As for your question about 'worth it to work in aRGB', it is a very valid to question the real value of exporting aRGB JPGs when almost all commercial printer output from sRGB files (those that accept aRGB files may actually convert the data to sRGB for printing!) and when most web browsers handle data which is in sRGB space
The fundamental problem (yes this analogy has its flaws, but it nevertheless helps with fundamental understanding of the issue...)
- imagine converting from counting 0,1,2,3...999 (numerical system A above) to counting 0,2,4,6...1998 (numerical system B above)...
and you lose all the odd values from 1 thru 999!
- imagine converting from counting 0,2,4,6...1998 (numerical system B above) to counting 0,1,2,3...999 (numerical system A above)
and you lose all the numbers from 1002 to 1998 because system A cannot count that high!
...so if you 'have to' convert all the time, aren't I leaving myself open to 'data loss' in counting?! So if you start with colorspace B and convert to colorspace A, aren't you losing some data when you started with the premise that it offered you 'more colors'?!
Yes, there is value in working in a 16-bit colorspace, and then outputting a different 16-bit color space file to print...like TIFF can be (but is not always) 16-bit color space. The disadvantage is the files are huge to transmit.