Answer
The two big differences are the change in Recognition (OCR) engines and the removal of the A2iA (check and handwritten data) engine and locator.
1) FineReader is no longer included in 7.0 as it was in 6.4. OmniPage is the only available OCR engine in 7.0.
It is possible to get the FineReader Add-on to add the FineReader engine, but this will only be supported to the end of 2025.
If upgrading to 7.0, the existing Batch Class/KTM projects should be tested thoroughly before upgrading a production system.
2) The A2iA engine is no longer available. It has been replaced by Parascript.
If making use of A2iA, the existing Batch Class/KTM projects should be tested thoroughly before upgrading a production system.