I used to gut every deer, then for a few years I did the gutless method. Now I'm gutting again, and here the main two reasons why:

Yield. I went from a little under 30% to right at or just above 40%. This is boneless and trimmed. The rib meat and meat along the ribs (breast and belly) make up a big part of this yield. That meat is excellent for grinding.

Innards. When possible, I eat the heart and liver. I do not count them in my yield.

Ive tried all of the methods above for opening the cavity, and the cleanest and easiest method I now use is to of course start with gloves. Next, before cutting through the abdominal muscles, I take a knife and cut through the meat down to the breastbone all the way to the esophogeal opening. I then take a saw and hold it upside down cutting through the breastbone. This will release the blood in the cavity if there is any and allow you to take out the heart. I saw up to the xiphoid process but not through it. After I have the heart out, I open up the abdomen with my knife and let the stomach/intestines/liver/spleen/kidneys fall down. I take out the liver, which is the hard purple organ (the soft purple one is the spleen) and place it in a separate bag. I then use my knife to cut the cartilaginous xiphoid and that drops the guts.

I've tried many other ways as I said, but a saw is the way to go. If you're in doubt, just go watch a video of a lamb being butchered. Commercial operations waste nothing and I don't see any reason why I should either. If the paunch of the deer has been hit by a bullet, meaning if a bullet has gone anywhere behind the diaphragm, I use the gutless method and avoid the tenderloins. Its just too hard to get the bacteria off and have a presentable piece of meat.