If its millions more, I think you need some sort of rational explanation before you invest in it. Think of how that money could be used elsewhere (union station anyone? Lower taxes?). I get the advantage of light rail when there's a dedicated right of way, but i'm talking about lighter than light rail buses. Not sure what Portland's situation is, I've never been there.
I agree about buses not being as sexy as streetcars, but i really think a lot of it is how they're marketed. I had no issue getting on buses in London. Look at the Boston system map. The silverline (the 2 spurs are to be connected) is a bus, but it has equal status with the light rail and subway lines on the map. It makes a big difference.
http://www.mbta.com/schedules_and_maps/subway/