Welcome to the world of posting and participating. Please do not be offended by my answer, it's nice to have you onboard.
Let me paraphrase your question:
I have a nice solid recording setup and have purchased an additional recorder. What i's like to do is either of the following:
a. Split my signal and get a probably slightly or greater than slightly degraded nearly identical signal into 2 decks, or
b. Output my recording into my second deck and get an mostly similar or identical but maybe slightly degraded 2nd recording.
I'd pick b. I guess, but really I'd invest in another set of mics, perhaps something different and/or a different pattern, and an additional battery box or preamp and make 2 different recordings each outing and see which I like more. (or maybe they are both so good, I cannot decide)
That is my 2 cents, welcome!