Should I get a iphone 6 or iphone 6 plus?

How much will both of them be on Black Friday?

You need to make your own decision on which of the iPhone 6 versions you want. Study all the differences.
It may come down to the size of your pocket. If they both sell really well, there may not need to be a black Friday sale.

Please don't mind, buy it at your own risk. Means, the mobile will be surely very sexy but on looking the specifications, I was very unhappy. It is costly both 6 and 6 plus, but apple often spend money on the looks of the phone and software. Not actually on its hardware such as processors etc. So I will recommend you to not buy either of them rather buy either htc or LG g3. ( on technical point of view)

When it comes to you, if you are apple lover I will recommend you 6 plus this is only because there's only about little difference between their prices (according to me) but a lot difference on basis of looks and hardware. So go with 6 plus. Be happy.
I don't know their prices on black Friday but, as I'm technician please wait a little or so when it will be available at market. I will be a way costly, more than 2000$ 6 not 6 plus. You can imagine price of 6 plus then. So wait till available on market.

TRS technician

Depends on what suits you, the prices vary per region check the apple site for prices they are there

It is best you decide yourself based on your needs, and other factors. If you don't have price problem obviously iPhone 6plus in the best.