Difference betwen two rear derailleur?
If the specs are identical, then they are functionally the same. There is no 'rotation angle' spec - the body of the derailleur rotates around the 'B pivot' and these two just happen to have been at slightly different positions when they were photographed.

The product names suggest the FT55 is slightly better than the FT35, but I don't think there is really any difference in quality between components in Shimano's Tourney range.