The weight increases efficiency by harnessing more of the bow's energy.You need to decide if the trajectory suits you.That setup will be plenty for deer at any sane distance you would normally shoot.If you decreased arrow weight to say 10 gpp,that would increase speed but would penetrate less.It would still be enough for deer.
Momentum is a good measure of penetration IF all other factors are equal.I worked momentum figures for one of my bows and the 10 GPP arrow had 19.7 % less momentum than the 13.47 GPP one.It is that dramatic and you can see it on game and in foam.