I've found joy and sorrow in both OB's and IB's.
Now you may not know this but I drink Japanese whisky from time to time
and there are no such thing as IB's unless they are bottled for the SMWS. They do however have a quite high proportion of single cask and cask strength bottlings in the OB ranges it seems to me in comparison the Scotch whisky.
I'd say conservatively 90% of Ichiro's Malts, 90% of Karuizawa's, 50% of Yamazaki's, 50% of Hakushu's, 50% of Yoichi's on offer are cask strength with a huge range of single casks. Now that is not to say that the majority of the actual bottles sold in Japan is cask strength, just that they offer a lot of them if you are so inclined.