If any of those 5 phones are basic phones, then yes, the old subsidized plans are better particularly if you take advantage of the fact that you can use the upgrade eligibility on the dumbphone lines and do a swap. While you are required to keep the upgraded line for the 2-years on contract ($10/line fee), you don't need to pay for "data" on any phone that isn't a smartphone. I did this before to upgrade to the new iPhone yearly. Alas, with the whole family moving to smartphones and getting iPads the new Mobile Share plans just made more sense.
Yeah, I've looked hard at the overall cost of the shared plan and unless I decide to convert at least two of my additional lines to a smartphone from a basic phone, it's not worth losing the subsidized lifetime plans even with the 2-year contracts. The $15/mo is very attractive, but that means you have to pay full price for the phone or an additional $25/mo per upgraded line (which you'd be an absolute fool to do).
If you are someone who doesn't necessarily need the latest just-released iPhone when it comes out, I can see the family plan being really good since you can buy a used iPhone for 1/2 the full retail cost. But since I'm an upgrade junkie, I think keeping what I have is the best bet for me.
You hit the nail on the head. As I assessed as well, as long as some of the phones on the line are basic "dumb phones", the older plans with contacts work out better. But if moving from a plan already loaded with smart phones or looking to convert some basic lines to smart phones, the new shared plans look to be slightly better.