I've fished rod & reel for over 50 years. I've spearfished (SCUBA) no more than 3 times in this last summer on the same wrecks I have fished for most of my life. First, for the primary species I am seeing here (tataug & seabass) I was amazed at how peaceful the fish have seemed. Little I did spooked them aside from sudden movements. As far as what is better for the fish, I'd say hands down spearfishing. While R&R fishing I catch a great many unwanted species and smaller fish. Most are wounded if not from the hook, but the rapid ascent where you can see the obvious barotrauma. Fish come up with eyes bulging, intestine bursting out of their rear cavity, swim bladder expanded out of their mouth. Many of these released fish, even after taking all the proper precautions (puncturing the bladders, etc) have a heck of a time descending and often end up seagull food before they get down. Only aiming at and shooting large fish, I dont have to worry about releasing unwanted catch. (Only once, my first shot penetrated a nice fat seabass and to my surprise had another small seabass also on the spear. I have to think this is fairly rare)
& then consider the commercial fisherman where is unwanted by-catch is measured by the tonnage.