post, "Length And Brevity," on the Poul Anderson Appreciation blog today, compares Poul Anderson's long future history, the History of Technic Civilization (seven omnibus volumes), with James Blish's much shorter future history, Cities In Flight (one omnibus volume).
There is much to compare:
"The Saturn Game" with "Bridge";
the Polesotechnic League with the Okies;
the Terran Empire with the Hruntan Empire;
the Merseian Roidhunate with the Vegan Tyranny;
the post-Imperial period with the post-Okie period;
also, Tau Zero (not part of the Technic History) with the post-Okie novel, The Triumph Of Time.
The point of the comparison is that both authors combined scientific knowledge with creative imagination and literary ability but that additionally Anderson was able to write a lot more. A bigger output from Blish would have meant not a longer Cities In Flight but completion of very different works like the unfinished "King Log" and "Breath of Brahma" and the proposed time travel novel.
Anderson also wrote variety, not just quantity. The Technic History could have been even longer but instead he went on to write the very different Harvest Of Stars future history.