I had the 30mm Eibach's and have swapped them out for B14's, so possibly a good person to offer opinion.
The 30mm's give a good compromise in that they give a slightly better look, and take some of the roll out of the standard height suspension (having used a standard height van for test drive for a day).
The B14's eradicate all body roll, whilst enabling you to run at standard height if you wanted to, or 60-70mm lower.
Yes they are expensive, however you get what you pay for, and personally I think that they are worth every penny.