Neither is rare although the Ko-sho is perhaps less often encountered in my view. As to desirability, it's really up to the individual collector and what they prefer to have in their collection. To me they both belong in a collection as a set. Much the same as would both of KVK2 With and Without Swords in a Third Reich medal collection.
I'm embarrassed to say that I was oblivious to the fact that there were both the ko-sho and sen-sho variants.
In general, Japanese medals are confusing and I think for most collectors, unfamiliarity with Kanji is to blame. A lot of vendors have no idea what they are selling and I've seen prices in a wide spectrum. For example, my wound badge was purchased along with other items for around $100. On the other hand, I've seen vendors selling wound badges alone for upwards of $500!
I'm very glad I purchased items from Japanese ebay. Pricing for militaria seems a lot more reasonable there. The only downside is added international shipping times.
No need to feel embarrassed. We all have to start somewhere. Consider acquiring the OMSA publication I mentioned above. It's worthwhile for anyone collecting Japanese military awards.
I'm looking forward to seeing what the postman brings you next.
Nice collection, I have just come back from a business trip to Japan, and I always try and time it for a local flea market (picked up a nice civil defense helmet). I'm always surpirsed by the quantity of medals available and kick myself everytime for not being better informed.
After seeing this I might start a secondary collection, at least they are easier to fit in the suitcase and less concerning for security.
Thanks for showing.
Very nice medal collection Joe. Now you need a Japanese golden kite medal.