24-70 CZ vs 16-50 SSM, A99 vs A77?

I don't know why so many people are talking about the A99 as an "upgrade" to the A77.

They're different - I would consider if you want to go crop or FF. The main difference in everyday shooting is probably DOF. And also zoom range. As an example, what appears to be the top "standard" lens for the A99 is 24-70. A zoom range of 3x. The A77 has 16-80 (5x) or the 16-50 which is 3x. I have an A77 with the 16-80 and don't see how an A99 would improve what I do. The camera's already far better than me - the shots that aren't as good as I want are down to user error, not camera error.

Decide what you want to shoot, and which is more appropriate for you - crop or FF. Obviously, you need to take your budget into account and there are also some tempting primes for the A77 - 35 f/1.8, 50 f/1.8 which are super quality. Also, you do get a built-in flash - even if you only use it to trigger other flashes.