Merry Christmas to you, Yaroslav!
I don't think there is a "one size fits all" solution. There are many factors to consider. Many involving personal choice.
I'm assuming here you are talking piano keyboard. Maybe it's the same for cba.
Are you used to a full sized piano? Then a keyboard with the same sized keys is good.
Same with if you are looking for a standard size so you can easily play many accordions you encounter. The experts here will know the most common size. I don't.
Are you looking to save weight and size? A more compact, smaller keyboard might be the way to go. Also if you have small hands, or shorter fingers.
Are you restricted to 41 treble keys, or would a lighter, smaller accordion with 37 (or less) keys be appropriate?
Basically, I think it comes down to getting the features you want at the size and weight you are comfortable with. I really haven't met that accordionist looking for a heavier instrument.
Imho, keyboard size (unless the keys are simply too small for your fingers) is secondary to accordion condition, sound, and features. At my age, give me the lightest accordion possible with a sound I like, I'll deal with the keyboard size.
Good luck!