I haven't seen the PA12 yet except in online media, so it's hard to compare the two. As was mentioned by a few other folks, you will have to look at the pros and cons of each and weigh them against what your needs and desires are.
1. The new seat looks really nice and inovative. If that really excites you the most, then go for the PA12. The PA 14 seat is still a great seat, especially with the adjustable base (if you add one). I've spent 6 hours straight in my PA14 and had no issues with the seat.
2. If you really want to carry your son with you, then maybe the PA14 is the way to go. It has 100 lbs more carrying capacity.
3. Weight - I'm going on 57 so I'm not as athletic as some of the younger troops out there, but I have no issues with my PA14 and using the bed of a pickup truck for hauling. It seems to me a difference of about 18 lbs between the 2 is not a determining factor.
4. Length - I have a 5.5 foot bed (F-150 SuperCrew). I can haul the PA14 without the t-bar extender if I want to, but use it on long trips from a safety standpoint. The truckbed extender only cost me $55, so it would not be a big expense. Both will stick out the back of any pickup truck.
5. Do you plan on mounting anything to the side rails? The PA12 rails do not appear to come forward as far as the PA14, so the mounting boards would be your only option if you want everything in your forward vision.
Just things to help you think about. We spend a lot of time trying to compare the two against each other versus what works for our needs. Yes I do like the looks of that seat and will probably sit in one the next chance I get. I hope I didn't ramble on too much...lol. Just my observations based on what I have seen so far. Both are great fishing machines regardless of which one you choose.
2013 Pro Angler 14 - Dune
2012 Pro Angler 14 - Dune