I don't mind paying the price premium for Quantum Turbo batteries. I had a couple of original Turbos that ran flawlessly for 12 years. There was cell replacement at around six years. I literally wore out the physical casings (leather back then...) They were replaced with Quantum T2 with the twin outlets. I have never been able to run this flat. having two outlets is cool if you're running two bodies with on-camera flash. I also have a smaller Turbo SC to keep power up to off-camera 580EXII.
When your professional reputation depends on having 100% reliable gear that you never, ever have to question, cheaping-out may lose you a client. That's much more expensive than paying a few hundred dollars more for the best.