IME 日本語文型辞典 has more entries, so it's more likely to cover the point you're trying to look up, but if Do*JG does cover something it typically has more detail and more explicit comparisons with other similar grammar (for instance DoAJG takes six pages to talk about 及び where 日本語文型辞典 gives it less than half a page).
I'd disagree with vix86 that "If your Japanese isn't spectacular already, there'd be no point in [this rather than Do*JG]" -- certainly you need some base level of Japanese (say at least making steady progress towards JLPT2) to make reasonable sense of the explanations and examples, but I've found it very useful in that intermediate and post intermediate level.
I'd disagree with vix86 that "If your Japanese isn't spectacular already, there'd be no point in [this rather than Do*JG]" -- certainly you need some base level of Japanese (say at least making steady progress towards JLPT2) to make reasonable sense of the explanations and examples, but I've found it very useful in that intermediate and post intermediate level.