I've only said the "L" word to a few people and meant it with all my heart. So my experiences are rather limited as to what to expect. However, from what I've experienced, and what I see go on, I'd expect that most submissives are more likely to share their feelings. Going a step further, I'd say most female submissives are more likely to share their feelings first.

In one relationship- he said it first, but we had been together for more than a year, after having known each other most of our lives. We'd started dating initially because we both had an interest in BDSM and had felt a connection. At the time he had convinced me that he was a dominant, though our relationship was heavily vanilla. (college roomies kinda squash the chances for a lot of things) Towards the end of the relationship, I had realized that while he can be dominant at times, his real preference was towards submissive. (way to go Jaina, skew the results by throwing a switch in there)

So, in that case, I think he said it first because he's more in tune with his emotions than most men I know. Is this becuase he has strong sub tendoncies? I couldn't say. My suspicion would be that yes, that is the reason.

Other times when I have been the first to say it to a dominant, it wasn't easy for me to say. I really don't like letting someone know how much control, power, they have over me. Those times, I said it because I was listening to my heart and knew I just had to say it. After saying it though, I always feel more vulnerable, open to abuse, and it took a lot of trust in the partner to know that they would not use my feelings against me.

I might be rambling a bit.. but those are what limited experiences I can add to this.