The truth is that it depends on a number of factors. Probably one of the biggest is my coworkers. In Colon, there was no question that we were a tight-knit group in the English department while the history department still seemed to be made of the good-old-boys-club. I liked both groups of people, but I certainly got along better with my English colleagues. At Lincoln, it was a bit of a reverse. While some of my best friends did (and still do) work in the English department, I often felt out of place (and sometimes unwanted) with the rest of the team. Again, I still liked the people in the department; I just didn't feel like one of them. The social studies department, on the other hand, ended up being a great group that I still miss dearly. In Skyview, I was part of a great team in the language arts department, but I wasn't really there long enough to make a comparison. Meanwhile, I'm still getting used to the waters at SoHi.
Another factor is the focus of the class. Despite my own writing history, I prefer classes in English that allow me to focus on the literature and what can be learned from it. Whether English or history, I dread teaching the hated research paper; instead, I prefer to make research feel like a more natural part of their learning exploration. I don't like teaching either if I have to deal with a group of students who are opposed to reading.
When teaching history, I like getting to tie in to current events and how things link throughout time. In English, I get to talk about the deep-seated human needs that are expressed in so many ways. With history, I get to play with charts, timelines, and maps. With English, we get to explore the creativity of our language.
I truly enjoy teaching both. History tends to get a little bit of a preference because the pressure isn't quite as high (there are few state tests that really emphasize history in facts or in skills). I try to keep students writing in both, but the pressure of paper correction is a bit higher with English as well. Yet there is a not as much poetry or lyrical quality to history; it's often too easy to get bogged in facts rather than deal with the larger concepts and the humanity behind them.
I'm glad that I've had the chance to do both.