I have owned a model M 172 and now a model F 150 and...
IMHO: The 172 is a more versitile, comfortable airplane and costs no more to maintain than its smaller sibling. Fuel burn isn't much different at similiar airspeeds but of course the 172 will go faster if you want to feed it. I would't even consider the smaller airplane for a growing family of 4. You'd find yourself flying alone or not at all having to worry about comfort, load capacity, and performance considerations. As for buying a 152 and renting a 172...WHY? (sorry fellas) that just doesn't make any sense to me. Buy a 152 and rent a 206 now and then, sure, but the difference in cost of ownership between the two is a Reallybignumber! 152 vs. 172 = A few bucks vs. Lots of advantages.
Of course, either way, you are required to remain a member of this club!! <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />
I agree with you Dan on everything except acquisition costs. Unless you are getting an early model 172 (O-300 powered), the acquisition costs are bordering on gold plated for a 172 (which seems odd considering their numbers). I was looking for a nice early 70's 172, and they were generally at or above a Cardinal with 180 hp and CS prop. The Cardinal has all the benefits in handling and fun factor that the 150/152 does, and will outperform a 172 (plus they look sexy), but I wasn't wanting to spend $50-75,000...so I am living with a Cherokee ($28-$40K for 150 or 160 hp and $38-50K for 180 hp). I will miss two doors, and the better interior space, but hey...I can haul half a ton in the Cherokee 180...no wait...MORE than half a ton.
Anyway...all that to say, acquisition cost differential would pay for a lot of rental fees and 152 fuel when comparing a 172 to a 150/152.