Going with a Softbank SH phone means you wont be able to surf the web nor download games unlike the Chinese phones. Therefore, 3G on Softbank phones doesn't really matter unless you do video calling... (the phones would probably connect to 3G if you're in a 3G area, but I dunno because it depends where you are). If these Softbank phones are eventually fully unlocked (which wont be for a while), you'll be able to download many games and themes that the chinese phones can't use.
When the 3G versions of the Chinese phones come out, expect to find them being exported at crazy prices. Unless you really need 3G, I'd wait for the 3G phones to come out and buy the 2G phones at clearance prices.
I don't know many retailers, but unless you actually go to China, expect to pay prices similar to the ones on Ebay... ($600-800 USD for either) The Softbank phones will run you about $200-300 USD less.
The 930SH (SH1810C) is superior to the 923SH (SH9020C) if you didn't know that.
Many of your questions were answered before...do a little more research next time.