I also compared them to what have been released before. The interesting subject I found was around the Panzer II. Althought Popy and Takara both released a Panzer II before, all three (together with the latest Dragon offer) were different versions.
The first picture shows (from left to right) the Pz. II D/E from Popy, Pz II F from Takara and the Pz II B from Dragon. Compared these to the reference book I have, I found they were pretty accurate. The II F was more an improved version of II B so there were more similarities between these two. The superstructure of II F was simplified. The new cupola shown in the II F actually can be found in some II B after an improvement kit was released in Oct, 1940. As you can see from the picture, the II D/E actually had a different designed hull, superstructure and suspension, but the turrent remained the same as the II B.
As shown in the left picture, the Pz II D/E on top had 4 big road wheels to replace the 5 smaller wheels in B or F. The return rollers were deleted. This Pz II D/E was not a mass produced model as only 43 were produced. However, it fits perfectly to Popy which normally only released experimental tanks in its Projekt Panzer series.