"ASK Haertel" on www.jamesblishappreciation.blogspot.co.uk.
Both Blish and Anderson:
were serious hard sf writers;
were among the authors whose series were edited by John W Campbell;
felt obliged to present new rationales for standard sf props like FTL;
wrote future histories;
speculated about the future of society;
were agnostics who took religion seriously;
also wrote historical fiction and fantasy.
Anderson was prolific, able to produce many works very quickly, whereas Blish's much smaller body of work was written at times, we understand, with considerable effort;
Anderson not only wrote both historical fiction and sf but also synthesised them in several works;
Blish managed to combine the three genres of historical fiction, fantasy and sf in a single trilogy;
Blish's sf series are more closely interconnected as he develops related ideas in different directions.