a murano is your alternative? eww.. i cruised around in one of those for a week. it was a horrible experience. how could a vehicle be sooo slow and unresponsive.. yet yield horrible gas mileage. there really is more space in my prius. it's faster too.
personally, i say go with something that is very fuel-efficient... whatever that means for you. then, if you happen to have a long family trip or something that you have several suitcases, children, boxes, strollers, etc then use the money you saved in fuel and rent a car/suv. the prius holds A LOT, as others have mentioned here. through the 365 days i've had mine, there was ONE time when i needed to borrow a friend's truck, and that was to move my bed and couches from one apt to another (cross-town). so basically, i needed a truck for a single 12 mile trip in a year...
I got 2 kids and 1 coming on the way (yepee), we fitted right now I don't know when the baby comes another car seat on the back with 2 strollers and baby stuff... Good thing we have a 4Runner with a third row
All I can tell you is that we commute everyday with our 2 and 4 year old and all their gear without issue. The kids seem to be comfortable and I haven't had a time where I wished for extra room yet, but... We have an 08 Honda Oddy EX-L w/RES for the times when we want real comfort and/or room. Sorry folks...regardless of the stigma...I still don't think a good, quality, semi-efficient minivan can be beat (although I hesitate to call any van built today mini). We're getting 26+ MPG out of our Oddy on highway trips...and although that is a far cry from what we'd get out of the Prius, we'll suffer the hit just for the extra room and comfort on the road. It's nice on those occasions when you've got to make that "don't make me come back there trip"!