Perhaps I am missing some, maybe someone else can fill in for me.

1. The soundboard material and supplier is different, and it is supplied to a higher grade.
2. The rim on the 168 is more massive, and the connection of the soundboard to the rim has been improved in order to contain more energy within the instrument.
3. The bridge construction on the 168 is different.
4. The bridge material is different.
5. The hammers are different.
6. The bass strings have been rescaled and are different..
7. The legs and lyre material is different, and it is now made of a specially treated wood aiming to prevent it from cracking even 60 years down the road.
8. The hardware is different, supplied to a higher grade by a different maker to prevent oxidation.
9. The plate on the 190 is of different design and manufacturer, aiming to reduce energy loss within the instrument yet to be stronger.
10. The plates are now finished much nicer, to a perfectly smooth looks.
11. There are now metal strips under the rear duplex aliquots to allow a tech to move these easier without scratching the plate.
12. The wood veneers used for the wood case pianos are of higher grade, and are now artistically matched to a very high level.
13. The finishes are better now (from the stand point of looks and durability).