Here are a couple of ideas. At one time, I practiced a style that integrated aikido, tae kwon do, and Okinawan te. As such we worked out with people from other backgrounds, especially tae kwon do and shorin-ryu karate.
As an unbiased observer, I would say that the karate people were very rigid, tense/intense, and deathly afraid of falling - I used to say they fell like trees, going down straight as a board.
Regarding the partner question you asked, my experience shows that these types of arts produce people who function at one or the other extreme - either they fully connect, as in sparring, or fully detach, as in the one-step and three-step form exercises, where the partner merely blocks or helps determine distance. There is no sensitivity or connection in the same sense as experienced in aikido. I'm not saying it can't happen; this is just my experience.
I have also engaged in sparring where the "uke" used only karate-tae kwon do attacks, and we as "nage" used only aikido moves. Want to know how really bad your aikido timing and responses are? Try it. It will shake you, and if you're courageous, you'll take it into account and practice better.