There are a few information about the difference. Because they use the same boards in both units, it must be the same source.

The MAX TNT was built to handle T1 speed per channel, povided by 4 boards with 8 ports and 24 channels with 56 kbit/s spped.

And the MAX TNT has one backplane-bus only. The APX seems to have two.

That was a weakness for the rest of the world (non US countries). All these have E1 as the basic pmx line speed. That means 30 channels with 64 kbit/s by 4 boards with 8 ports.

There was a solution to connect 3 MAXen together to be one unit. Only a few large provider did install this and evaluate the weaknesses. A TNT was 150.000 dollars and up. Read the rumours from the Ascend internals.