Lots of variables in the equation, heavy arrows have more penetration which is a good thing to a certain point. A light arrow with a good sharp COC head will still out penetrate a heavy arrow with a large surface area or mechanical head. It really just depends on you, your mentality as well as what and where you will be hunting.
I have shot and killed elk with super light arrows and pretty heavy arrows. I'm currently shooting a 500gr arrow with a large cut expandable head. I have a ton of confidence in the arrow combo, it flys like an absolute Lazer and is devastating when it hits. I'm also shooting that arrow 285fps ish.
Your setup will kill any animal just fine and if you really don't feel confident or good shooting the heavy arrow then switch back to the 400gr or maybe split the difference. Bruce commented that about 3D archers wanting the lighter arrow to keep their scores up, I can tell you that when I shoot a 400gr arrow my 3D scores are way better than when shooting 500gr. 3D is just foam but you are shooting unknown distances at animal sized targets, you hit where you are aiming less with the heavy arrow unless you know the exact yardage. If you feel like you will be able to only take shots that you range then it doesn't matter what you shoot. If you feel like you will feel pressured to make the shot and don't have the self-control to possibly miss out on the buck of a lifetime because you didn't get a good range on it so you had to pass then maybe you would benefit from the better trajectory.
If you hunt in super heavy cover where shots are not likely past 40 yards then it doesn't matter and you might as well shoot the heavier arrow that will have more momentum, quiets down your bow and is more forgiving to fixed heads. If you hunt open country, you feel like you will be taking longer shots and may not have time to range and feel like you need more speed to make up for your misjudgment of yardage then stick with the lighter arrow. Either will kill an animal if you put them behind the shoulder.
I like ending up in the 280-290ish range for speed, if I get much lower I am unhappy with the trajectory when I'm up over 300fps I have a harder time getting fixed broadheads to fly well at longer distances.
There is no such thing as too slow or too fast, figure out what you like the best and shoot that, there are always trade-offs in archery. Confidence Kills!