First things first:
Make sure all these options are your true size.
Do not start to training in the bike without a proper bike fit.
105 groupset is quite heavy, if you can avoid it and get a Ultregra your life is gonna be better!
I would say an Argon18 E-117 has a nice aero frame for the value. Could be my first option, but it the Cervelo P2 is not a bad option in the end. The issue here is that groupset has come with Cervelo is pretty terrible compared to a new E-117
ps: Do not avoid make a bike fit before purchase the bike, if both are in the same store maybe you can try it