Dan-cer
the obvious answer is the phone you can comfortably afford, and I don't mean the phone you can buy and have no money left, but the phone you can buy and if needed, replace if you lost it, etc.. because you have money left.
your choice was a 7 series or 8 series.
7 series are EOL in about 2+ years
8 series are EOL in about 5+ years
Are you ever likely to still have your second hand phone in 5 years time?
Read the threads in this forum, Pixels are prone to battery failure, have heating issues and some hardware that seems fragile.
You might even drop it on the day you buy it!. remember the person who bought the first new apple phone in the UK at midnight, and was filmed on TV opening the box outside the store and he dropped it...
I personally would buy a Pixel for as little as I can from a reputable online store that has a good history of customer support and returns, not the one with this months amazing one off deals never to be repeated, etc and no contact details.
its just my opinion.
After all its your money and spend it as you will