Reading them both is valuable for the lessons they teach. Having them as favored reading material changes the perspective. Certifiable nutter remains an apt description.
And yes, Tom, they are tough to read through. And, you are right that the two philosophical perspectives get pretty ideologically close when taken to their extremes. And, neither Marx nor Hitler were worth a look (ugly, old, and male). Ann Coulter is hot. And that's where FQ misses out.
True, but that's not where I was going

Hitler and Marx wrote long winded political rants that were meant to be shouted from a lectern, like Castro's speeches. They are not meant to be "read", they are meant to pummel your brain into submission.
Ann Coulture writes books that through the use of wit and sarcasm are meant to keep the reader entertained long enough to get her point across.
As to the 2 ideologies the difference is in the focus "Communism" is "international" socialism, focused on a world wide scale, while the Nazi's intent was to apply the socialistic principles only to one nation.