I haven't shot the 2013 Nemesis, but shot one a few years ago. I liked the looks of the Nemesis a little better, but wasn't willing to pay the price difference just for the looks. The Onza shot just as well for me. Just as quiet, smooth, and fast. My 70# Onza was getting 302 fps with a 386 gr. arrow @28 1/2 draw at 70#. At least according to my chrono. It may be off a bit, but not much. It usually checks out with the one at my local shop.
I'll keep hold of the Alien until I hear more from you. Thank your buddy for me.
Eric
2006 Rytera Bullet X 60#---2008 Moab 70#
2008/12 Firecat 60#--- 2010 Warthog 70#
2010/2012 Alien X 65# 2011 Onzas 60 & 70#
2009 Warthog 70#---2009 Firehawk 70#
2010 Strother SR-71 65# & 2012 Strother Rush 65#
I hunt, therefore I eat. lol