IMHO, what matters most is a sharp c-o-c broadhead AND consistent accuracy whilst on the hunt.
The ability to consistently deliver a lethal blade in the right spot, with "hunt shooting form" and not "target archery shooting form", makes for good kills. Knowing your maximum consistent hit range is also important. This is where heavier arrows will have increased arcs that might mean 10-17 yards is almost a gimme while 20 yards and beyond might be a "hail Mary". The important part of this equation is you, the bowhunter, and how effective you are with controlling bow holding weights. This can only be discovered by practice hunting.
Arrow weight is important. The rule of thumb has always been around 10gpp, i.e. - a 500 grain arrow for a 50lb bow holding weight (not draw weight). This is not a hard 'n' fast rule and is surpassed by consistent accuracy at a specific kill range. Light arrows would not be a good choice because while they will have a lowered flight arc, they will lack in penetration, even of their broadhead is truly hair shaving.
In the matter of broadheads, I've found the easiest for anyone to get razor sharp are good three blades such as the venerable Wensel Woodsman - lay flat on a file or sander belt and the blade angles are always spot on (see Charlie Lamb's How-To tip at the TG resources board). Arrows kill by blood loss, not shock. The twin or four blades will require some manner of understanding and retaining proper blade angles. If I can't create razor sharp broadheads, I ain't going hunting.
Good arrow flight that will deliver the cutting edges straight, not with any fishtailing or porpoising, is also important. This means both arrow spine and string nock placement and type of arrow rest and fit of the arrow nock to the string. Add in shooting form, or lack thereof.
Over the decades I've had to drop down in both draw length and holding weight, and these days for 28@43 my completed woody arrows (broadhead or field/blunt point or judo point) are around 520-540 grains. The rest is up to me.