Transformers are bulky, clumsy, not always that easy to transform (in fact, when they've tried to make them incredibly complex/accurate, they've been unnecessarily complicated (see Alternators)), they often use Die-Cast poorly (see MP Prime), and usually don't look incredibly like either a robot, or their alt mode, usually it's one or the other.
On the other hand, Yamato, and Bandai, have given me toys that look very much like all three modes they convert to, are generally sturdy and look gorgeous on my shelf.
To further evidence, the greatest Transformer toy ever was Jetfire, which was a Bandai Valk with an Autobot sticker.
I like Transformers, and they have their place, but I think my Yammies are way better, at least for my tastes.
Remind me again why I'd want valks to be more like Transformers?