I bought a maxed out 2016 MBP with touch bar to upgrade from a 2012 MBP.
I'm currently working from my maxed out 2012 MBP...
Here's some notes that may help you in making a decision:
The performance of the 2012 MBP after upgrading to High Sierra is very similar to the performance of the 2016 MBP on the original Sierra. Geekbench showed around 400 points difference between the two (which is nothing really).
If you're looking to play games then there's no comparison - the newer MacBook Pros graphics cards are much better.
I miss having Thunderbolt 3 USB-C ports. I have many USB-C cables and accessories now as well as an external graphics card. I don't miss having MagSafe even though I thought I would. It's quite nice to not have the power disconnect without me realising. Having a single cable to my monitor is also pretty great.
I also miss Touch ID but while I tried, the Touch Bar itself was only really used for media scrubbing...it's just not a natural user interface.
I ended up using and preferring the 3D/Force touch trackpad more than I expected. I much prefer its size in the 2016 MBP too.
The 2016 MBP speakers are a lot better but I use external speakers and headphones anyway. It's also enough lighter that it's definitely noticeable on your back. It's quieter too.
If you copy a lot of files to/from the MBP then the newer SSD's can make a significant difference.
I've found that I don't miss the extra colours in the newer screen, nor the extra brightness of the display.
They 2016 and 2017 keyboards feel pretty similar - I personally prefer the shallower keys of the Magic Keyboard they sell separately but there
The 2016 MBP just doesn't handle high-cpu usage very well and it seems the same applies to the 2017. Keys become sticky at different temperatures, some keys become harder to press depending on the temperature and it's even warped the screen a bit (I'll be on my third 2016 MBP soon). Press hard enough on the return key and it will interfere with the fans underneath...that's how little space there is. You can also literally bend the laptop enough that different keys will be harder to press depending on how you bend it (without much pressure applied). There's times where I'll lean either side of the trackpad while it's on one new (like in bed) and it ends up causing issues with the keys.
The 2012 MBP certainly doesn't last as long in terms of battery, largely because the battery is so old.
From the above you may expect me to recommend the 2016 over the 2012 but ultimately I regret buying the new laptop - it's not worth the money to upgrade. Thousands of dollars for what comes down to a larger trackpad, Touch ID and slightly better battery life. The issue with the keys has been a deal breaker for me.