Spoiler alert! [
For E.E. 'Doc' Smith's Lensmen series]
Spoiler:
There aren't any major difference, at least until later in Gray Lensman, but a number of phraseology changes, and a lessening of the Arisian appearance of competency. They are still really smart, but nearly as overpowering as in the novel version.
Several general examples of changes:
Galactic Patrol: When Kinnison captures 6 Boskonian ships, the surviving crew of Britiannia are scattered among the 6 ships, rather than being concentrated in one ship of the 6 in the novel.
Gray Lensman: in the torture scene with the Delgonian Overlord, Kinnison ends up physically fighting the Overlord, (completely implausible!) rather than having the worm switch off the thought screen. (obviously an editorial re-write, and a clumsy one at that!)
No major scene omissions or insertions, just editorial steeping on various scenes, from trivial to major.
I haven't started on Second Stage Lensmen yet.