Truth be told I do find myself using both for the reasons you listed. Now if he ever reformats it to more of a dealer type page set up where you can click on the year and see the thumbnails to the variety I may go ahead and ditch the book, the drop down menu can get tedious when you're don't have a general idea of what ones it should be. I do really like the larger color pictures on the site though
I recommend Roger Burdette's "From Mine to Mint" which covers every step of the coin manufacturing process in the 19th and 20th centuries.
What it *will* do is replace Heritage as my cross-reference for what I determine from Overton. My attribution habit for Busties is to utilize Overton and then pull up high-res images from Heritage to compare features like letter alignment which is less-clear in the small Overton images. Busthalfaddict's site will make that process far more streamlined and his images are good.