I guess you got that paragraph from this page..
http://www.tciauto.com/tech_info/torque_converters_explained.htm
From another paragraph there's this sentence:
".. A more detailed discussion of torque multiplication can get very confusing to the layman as high multiplication ratios can be easily considered the best choice when in fact more variables must be included in the decision..."
They do not elaborate on what those "more variables" are.
So it seems like choosing a converter to fit specific needs is not something the "layman" can do as well as a pro could.. I'd try calling that company and asking who can do all the calculations for you.
From what i gather (and this is all new to me) there is no downside to a higher stall speed IF the converter was properly chosen FOR a particular set of driving conditions..
On the other hand, if you are set up for drag racing and try to drive in bumper to bumper traffic, there's gonna be a downside.