I'd much rather have a #1 seed than a #1 ranking. The rankings dont mean anything at all.
That being said I don't see how Iowa gets a #1 ranking or even 1st place votes without winning at least the next 4 in a row. That probably still wont even get them there without lots of help.
What percentage of 1 seeds come from teams ranked in the top 4? I'm guessing it's pretty high. Rankings matter. They matter to the selection committee, they matter to fans, and they matter to recruits.