Just to throw a spanner in - the labs mentioned are good but not necessarily the best or most cost effective.
I used Pro Am for years and it doesn't come up to the standard of
DSCL it terms of speed or cost or quality.
Also sending out isn't for everyone - I print everything larger than A4 on an Epson 4880 and the costs when buying wisely using genuine ink run me at 1.50 for a 16x12 (size of my album layouts).
So there is no one right answer