[nikeshm]

Echoing what a lot of other posters are saying, I would strongly recommend considering advisor/group fit. Of course, research field also matters; it seems like you don't really like networking/security that much, so feel free to steer clear of those disciplines. However, let's say you meet an awesome AI prof, and their work is of moderate interest - that seems like a recipe for a good time, even if the field is saturated/there's an AI winter in our future.

Anecdotally, my first research position was the result of getting my last-choice internship for that summer. I thought I would hate it and was planning to quit after the summer. My advisor was incredible, and I ended up working in that lab for 3 years. That field (human-computer interaction) is now my primary discipline!