What sound do you like?
The model numbers matter too, as the Yamaha C or Kawai RX are far better than the lesser priced models.
What do you like about Boston? The big fat bass perhaps? If so examine the Tenor and Soprano range for singability. A lot of the times I've found these parts of the piano rather underwhelming.
Do you like the colorfulness of Kawai's tone? or perhaps the clarity of Yamaha?
If you are attracted to these pianos by brand name alone, I suggest you keep looking around. Make note of properties of a piano you are attracted to rather than name or prestige, and look for them in any brand you may be considering.
What would you like to hear, touch, feel and experience in a piano that you own? What music do you play?