Both are great quality prints, and the best prices I've found online. And you upload the files directly to their website, and even get proofs online. I've worked extensively with 4over4.com, and can vouch for their professionalism, customer service, and great quality prints. Oh, and they're way cheap!
did a great job on my postcards...they were printed in 24 hours, UV coated and cheaper then other printers i researched online. they also answer the phone everytime i call.
800printingnyc.com did an amazing job with the design of my club flyers.
they printed 5000 4x6 flyers in 24 hours and i had their delivery guy deliver it to me in NYC. They always pickup the phone and very helpful.