Expect the best. Your digital files have been color corrected and post-processed in Photoshop with great care. In the files, "metadata" is embedded that tells a lab how the images should be printed and color calibrated to match what we saw on our screens. A professional level lab will read that data and print a product that is on par with our expectations. A consumer level lab (Walmart, Costco, etc) operator is typically not trained to read this data or adjust the machines to appropriately print the files. That is why coloring and quality can vary greatly when using a consumer lab.
Printing with our professional lab ensures you will receive a product that matches what we produced for you here in studio, and it also ensures your prints will be of archival quality and last for generations. A quality, printed image is an heirloom.