This question has been discussed to death in the past. Unfortunately, the forum search feature is a bit too feeble to ferret this one out to the discussions being ancient history.
Originally posted by house From the simple scaling and overlaying of the two lens diagrams it seems the glass elements are larger on the 2/35. I will have a look at comparing photographs at a later point.
This is obvious with both lenses in hand and has been noted in the past. They are similar in the same way that the DA 50/1.8 and various 50/1.7 lenses are similar. Quite simply, the HD DA 25/2.4 is not a less expensive version of the HD FA 35/2 on FF or on APS-C.
As for assessing the DA 50/1.8 on FF...I did so on 35mm film and it flunked. Similarly, multiple other users on this site have compared both the DA 50 and DA 35 "plastic fantastics" with same focal length equivalents with the general consensus being that that vignette and fall-off of image quality does not warrant use of either lens on FF except for novelty or if "cropping to quality" is the intent.
Since it appears from the comments above that you already own the DA 35/2.4 and are shooting FF, you could simply try it for yourself on that camera. If the results are subpar, the FA 35/2 or FA 31/1.8 Limited might be good options.
Steve