The best writer, by far, is Luksa, followed by Galloway. Unfortunately, their opinions carry little credibility, and they don't even try to be reporters (ie., gathering and reporting information).
Gosselin is by far the best reporter and is a good writer. But he has too many times when his evaluations are not only laughable, they're based on entirely faulty logic. If he shared his sources' opinions all of the time and his own opinions none of the time, he'd probably be the most useful NFL writer in the country.
JFE and Hill are decent reporters and average writers. JFE's problem, which is evident if you listen to the press conferences, is that she seems to choose a topic, then fish for news about it -- instead of vice-versa. Hill is mostly innocuous, but he has occasional flashes of brilliance. Neither of them shares their opinion very often.
JJT is a mediocre reporter, is a below-average writer and has mostly worthless opinions. Why a paper like the DMN hasn't replaced him yet is beyond me.
Spagnola is a below-average reporter (or maybe he's just kept on a leash as a team employee), is an embarrassingly horrible writer and has tired, predictable opinions. Eatman is an average reporter, is a below-average writer and doesn't share many opinions. Chad/Dale honestly seems to be the best writer at the official site. (Now let's see him get a crack at reporting and opinions.) Chad/Dale also seems to be one of the few who understand what fans want to see from a training camp daily report -- probably because he's the most in-touch with the fans.
Anyone else -- I really haven't formed an opinion yet.