In which part of Osaka are you working? (What are the closest stations?)
Which airport(s) are you flying into and out of?

Once you know which places you're going to need to access, it's possible to narrow your choices.

If you read Japanese, there's a good "ranking" of business-hotel type places (in the 10,000yen - give or take a few thousand - price bracket):
http://www.jttk.zaq.ne.jp/baaoi603/hotels/osaka.html