"The eternal conflict of publishing books is that, if you start a series like this from a #1, some readers will be angry and ask why you did it. And if you continue the numbering, some readers will be angry and ask why you did it. So in each case we make the decision that makes the most sense to us, that we think is best." Red She-Hulk was a completely new and different book from HULK which it continued it's numbering from though. Only thing they had in common were that they were related and red

Anonymous
There was more than that, including the same creative team and the continuation of plot elements and characters from the Red Hulk run.