If your working with a 5% discount, I would just forget about the 2013 and go for the 2014.
Will you have quality issues, I hope not, however prepare for the worst, hope for the best.
Yes the motors may be coming off the current engine offerings list from BMW, and the platform maybe a stretched version of the 5, but at the end of the day:
1) ITS NOT EXACTLY THE SAME VEHICLE AS ANY CURRENT BMW, SO YOU CANT EXPECT AMAZING RELIABILITY FROM THE GET GO!
2) Did you walk perfectly the very first day you were born, same applies here.
3) This aint a toyota moco vehicle, where the tech is tested through various brands, many vehicles, and years. So expect quirks.
If your going to lease, forget about everything, you are only gonna have it before the warranty expires.
If your going to buy, and keep longterm then i`d be concerned (check out the launch vehicle owners of the E70 and their unique problems)
BMW and Mercedes Build Beta Products!
Lexus build Release Candidate Products!
Why does this matter?
CAUSE EVERY TIME someone says Lexus has better build quality, one should consider what Toyota their Lexus Engine and chassis platform comes out of and how long that part has been tested in the real world!