Well, I put DS in trainers around 7.5 mos and I really like them.
I had a few reasons. We were using pre-fold diapers and he was outgrowing the size we had and the size up seemed SOOO bulky for him as he got more mobile. I didn't want to spend a ton on pocket dipes either. Also, I did like that they are not bulky like a diaper. I also liked that it made me more mindful when he was in them as I know that I need to check often as they only hold 1 pee (but a good size one!). Also, I actually find it easier to pull them up and down than to try to get him in/out of his diaper! He will NOT stay on his back, he always rolls onto his stomach. If your DC can stand up, it is especially easier to potty them if you are out of the house as you can get them to stand on your lap or on a bathroom counter, etc. and just pull them up! No need for a change table.
However, if your DC is not really good with poops, don't do trainers!! We have very few poop misses but when we have it is an automatic bath for DS because I need to pull them off and the poop tends to get on his legs and be a bit of a mess. Other than the poops though, I love them (and they are sooooooo cute!!).
Oh, also, they take less time in the dryer than diapers!