i have always shot xx78 2315. they have never let me down and my magnatec set at 66 pounds and is one of the quietest bows that i have ever heard. this setup is not the fastest i think i was getting like 225fps.
bought the ultratec this year and decided to try goldtip xt so far i like them although there is more string noise involved and roughly 50 fps increase.
this was a tough decision for me to make. the 78' s did every thing i asked from them and i do not think you will have any problems goine to alu. i think they are a lot more durable than they get credit for. yes they will bend but i can afford to bend an arrow when i have meat in my freezer.
i just hope i did not make a huge mistake going to the xt' s this year. hope this helps.