gistfile1.txt

They both write the same value when the node script uses a Buffer.

~/Downloads/2010-05-07/compatibility_issue ⚡ redis-cli flushall
OK

~/Downloads/2010-05-07/compatibility_issue ⚡ !node
node write_file_to_redis.js 2> output.node

~/Downloads/2010-05-07/compatibility_issue ⚡ redis-cli get test_key
"\x1f\x8b\b\b\x80\xce\xe3K\x00\x03testfile.txt\x00\x0b\xc9\xc8,V\x00\xa2\xe2\xfc\xdcT\x85\x94\xc4\x92D\x85\x92\x8c\xc4\x12\x90Hz~f^\xbaBI\xbeBR\xaaBr~nAQjqqj\n\x17\x00\xc8\xcerT1\x00\x00\x00"

~/Downloads/2010-05-07/compatibility_issue ⚡ !python
python write_file_to_redis.py > output.python 

~/Downloads/2010-05-07/compatibility_issue ⚡ redis-cli get test_key
"\x1f\x8b\b\b\x80\xce\xe3K\x00\x03testfile.txt\x00\x0b\xc9\xc8,V\x00\xa2\xe2\xfc\xdcT\x85\x94\xc4\x92D\x85\x92\x8c\xc4\x12\x90Hz~f^\xbaBI\xbeBR\xaaBr~nAQjqqj\n\x17\x00\xc8\xcerT1\x00\x00\x00"

~/Downloads/2010-05-07/compatibility_issue ⚡ diff output
output.node    output.python  

~/Downloads/2010-05-07/compatibility_issue ⚡ diff output.*

~/Downloads/2010-05-07/compatibility_issue ⚡ echo $?
0

gistfile2.txt

with some changes, it works the same for binary strings:

~/Downloads/2010-05-07/compatibility_issue ⚡ redis-cli flushall
OK

~/Downloads/2010-05-07/compatibility_issue ⚡ node write_file_to_redis.js 
len = 78

~/Downloads/2010-05-07/compatibility_issue ⚡ redis-cli get test_key > a

~/Downloads/2010-05-07/compatibility_issue ⚡ python write_file_to_redis.py > output.python

~/Downloads/2010-05-07/compatibility_issue ⚡ redis-cli get test_key > b

~/Downloads/2010-05-07/compatibility_issue ⚡ diff a b

~/Downloads/2010-05-07/compatibility_issue ⚡ echo $?
0