cheltzel

If you want to be in the city center and convenient to the Blue Line, you have the following options:

Westin Chicago River North (3 - 4 blocks from Clark/Lake)
W Chicago City Center (2 blocks from Monroe/Dearborn or 3 blocks from Jackson/Dearborn Blue Line)
Renaissance Hotel Chicago (2 blocks from Clark/Lake)
JW Marriott Chicago (3 blocks Jackson/Dearborn)

There are other very nice hotels in the Michigan Avenue are but these are really not convenient for the Blue Line. You would need to take a cab from the Blue Line to the hotel (unless you don't mind hauling your bags on a 6 - 9 block trek from the nearest Blue Line station in the middle of a Chicago winter).

If you want to a convenient location for the River North and Michigan Avenue areas then you would look at either the Westin River North or the Renaissance Hotel Chicago. If you are more interested in the Loop area then you might focus on the other two.

I have not stayed at any of the SPG or Marriott properties downtown but have been at meetings and/or events at most and they all seem very nice. I think your are going down the right path by digging in to the reviews for the properties. Just narrow the field down by your geographic requirements and don't waste time on ones that don't match your requirements.