Both have their pros and cons. I was with both and here are my results based on service in Northeastern PA.
Netflix was with for 8 months:
First 2-3 months many new releases, then the dreaded throttling occurs once they get a read on your rental habits. Then all new releases on a long wait for at least one month. Every movie with the exception of new releases always available. Followed your queue ranks with available now titles(more on this with Blockbuster below). Shipped fast, got movies within 2 business days. Only averaged 9-10 movies/month on the 3 out at a time plan. After about 5 months I started getting in alot of busted DVDs or severely scratched DVDs causing further delay in getting replacements for the movies. These were older movies mind you. Got feed up and tried Blockbuster online for a free one month.
Blockbuster with currently for about 7 months:
First 5 months many new releases and the 2 instore coupons/month fabulous. Very few movies were on any sort of wait, maybe 3 out of 40 but none of them new releases. Lately though I am considering dropping their service as I can almost never get a new release even a month after it is released due to a suppossed long wait. I use the 2 instore coupons for these must see ones. Average about 9-10 movies/month on the 3 out plan. Also, Blockbuster seems to jump around your queue alot by bypassing higher ranked available now titles many 4-6 places up over lower ranked available now titles(all of these are older titles). Also Blockbuster averages an extra business day to get the movies than Netflix, but at least they do not come in busted or severely scratched.
Conclusion:
Neither service is great after about 5 months unless you seem to stay under about 8 movies/month averaged or throttling seems to occur. I am seriously considering going with the Hollywood Video unlimited rentals/month plan and get what I want on the spot without the wait. But if I had to pick on I would go with Blockbuster not just due to the coupons but the quality of the discs.
Cliffs:
Pros
Blockbuster
Better Quality Discs
in store rentals
wait longer to do some throttling
Netflix
Faster Ship Times
Better Selection
Follow Queueing