difference between V-てばかりいる and V-てばかりだ?


What's the difference between V-てばかりいる and V-てばかりだ?. I came across these
sentences and they seem to have all the same meaning "always/only be doing
something", but their usage and constructions appear to be different:

> "幸子ちゃんは、毎日食べてばかりです。"  
>  "幸子ちゃんは、遊んでばかりいます。"  
>  "幸子ちゃんは、泣いてばかりいて、何も話そうとしない。"




The only difference that I think might be worth mentioning is that:

> 「～～てばかり+ **いる/います** 」

sounds **_slightly_** more formal and/or objectively observed than:

> 「～～てばかり + **だ/です** 」

which could tend to sound **_slightly_** more subjectively observed,
emotional, exclamatory, etc.

The difference would mostly be minimal unless these phrases are qualified by
other words used in the context.

