Spencer,
When my daughter was little, I had a rear child seat that attached to my rear rack. She loved it and we both enjoyed biking about immensely. However, when she got a little bigger, sometime between age 2 and 3, we had to get a trailer. She was just too big for the seat. My concern was that if you laid the bike over while underway, her little body wasn't fully contained in the seat frame any more, and some serious road rash would result.
The trailer I purchased was great, but it did slow me down a lot more than the rear seat option. Positives included the ability for my daughter to carry all kinds of snacks and drinks and have them immediately handy, no possibility of scrapes or bruises, a larger profile to make it easier for cars to see us (gravel roads/back roads only, however). Downsides for the trailer I purchased anyway, was little protection from chasing dogs (daughter was usually armed with rocks), less cushioning, and the inability to lay the bike on it's side while the trailer was attached. If I were purchasing a trailer now, I would make sure that it provided complete protection in front from flying rocks and insects, was completely enclosed for protection against animals, with netting in front/back for cooling, and had an attachement that allowed the bike to be laid on it's side. The better ones used to attach with a universal joint on the chainstay, don't know about now.
I wouldn't worry about not being able to communicate. We never had a problem, and the trailer I had required the child to sit facing backwards. I imagine a trailer that allowed the child to face forwards would facilitate communication. We usually saved the talking for breaks and just enjoyed the scenary.
One last recommendation. Buy a couple of those battery-powered LED taillights that constantly flash. The batteries last a long,long time and they make you more visible.
Oh, and I always insisted my daughter wear a helmet, even in the trailer.