I suggest getting a copy of Aaron Shepard's Aiming At Amazon and reading that before making a decision. No matter who you go with, plan on hiring an editor/proofreader. (Check prices in Literary Marketplace against what self publishing companies - including Lulu.com charge.)
Often you can find higher quality editing services at a lower price than what the self publishing companies charge. Aaron Shepard suggests going straight to Lightning Source (which is who Lulu, Createspace, and others use) yourself. Lightning Source is owned by Ingram, so you will be listed in their database.
If I had to choose, I'd go with Createspace and use my own ISBNs due this being Amazon's self-publishing arm.
Regardless of who you choose, plan on having editing done yourself and getting your own ISBNs.