This is great piece by Gregory Lehman and though a long one well worth reading it all. He looks at the pros and cons of maintaining a neutral spine and allowing spinal flexion to occur. Needless to say the case isn’t clear cut and it depends on your goals, tasks you require to do amongst other factors.
http://www.greglehman.ca/2016/01/31/revisiting-the-spinal-flexion-debate-prepare-for-doubt/