I doubt you shoot the lighter bow better because it is lighter. Sounds to me like you shoot the heavier one too much. Shooting too much can be a problem and more than likely to cause injury than shooting more weight. You have to be honest with yourself, are you really comfortable with the weight? or are you looking for a reason to shoot less? Repition is far more likely to wear out the joints.
Whatever you decide to do, that will become your max comfortable weight. Your muscles will atrophy to what ever you are willing to work too.
Yes, lighter weight bows are capable of doing the job and so are ugly women and old slow cars, but heavier bows just feel better (if you are comfortable with them)
If you are truly comfortable with the heavier weight, you can easily find a bunch of people here to tell you that you can't do it! After all, taking the work out anything is the american way. Don't do that extra work, you can surely find some way to get out of it.
You have lots of years ahead of you to slow down. You are young, and god willing, you will live to be old. Slow down now and you will be less for the rest of your life (not just draw weight* be honest with your self about that and quit listenting to popular belief).
I have broken my neck, shattered my rist and forearm, shoved my thigh bone through my hip socket, damaged my rotator and am still here. I am 43 years young and have no intention of slowing down until I have no choice. I will slide in to my grave as a worn out, broke up mess weather it be tomorrow or 50 years from now.
I am honest with myself about what I shoot for weight (what others think makes no difference to me) I love the feel of the power and the force of a 800g shaft crashing through a critter. I shoot whatever broadhead I like and don't ever worry about if I had enough!
I have now used up my alotment of typing for a given week. Good luck to you in whatever you decide, but do it for the right reasons.
Bigjim
Oh yeah, this bow order won't likely be your last. If you enjoy this sport, there will always be another.....you are young and bows are not women. We don't have to pick one to spend the rest of our life with.