Having only visited Brisbane but living in Tas, I disagree, I really can't see many similarities between the two.

Very different climate
Very cold sea in Tas most of the year
Very little choice in the way of shopping, one small department store in Hobart compared to large shopping complexes in and around Brisbane
Limited choice of entertainment for kids in Tas, ie no theme parks, water parks etc (might not be a bad thing depending on your tastes but with 2 older children we do find Tas a bit limiting for family days out, we love walking but not all kids want to do that every weekend!)
Less employment opportunities simply due to less people
More of an island (and at times backward) mentality in Tas
Easy to get away from the crowds in Tas, even on public holidays, higher population density in Qld makes it less easy, though not impossible of course!

I could go on but I really do think the two places are poles apart, both had their good and bad aspects just like anywhere in the world, depends what you want and your own circumstances really.

Sam

I was responding to "Brisane and Tasmania are probably about as different two places can get in OZ."...I agree, most Australians cities have those differences you listed with Tasmania but I don't think it is the "most" different for the reasons I outlined.

Oh, I see what you mean! Yes, there are maybe cities that are even more different in comparison, like Sydney for instance.

But to get back to the original point, I think that if you like the look of Brisbane, then it's a big shift to change to Tas! We have neighbours who moved to Tas last year after visiting many times, they had lived in Brisbane for 3 years and just couldn't take the heat any more. Anyway their house is now up for sale and they are moving back, the husband has got his old job back and they can't wait for the warmth again!

Sam