Is the capital-output ratio in developing countries low or high?
The key to the answer is good data on Capital. There is a project (KLEMS), which is computing harmonised (i.e. comparable) information on capital, labour, energy, etc for many countries. At the moment it has information mainly on developed countries, but data for more developing countries are coming up. 

For example, this is a calculation of the capital-output ratio for the case of the UK:



For the case of developing countries, here is a figure:



(source here)

It seems that developing countries might have lower capital-output ratios. However, this is ultimately an empirical question which requires a proper analysis. I suggest you use the KLEMS data to make your own, harmonised study.