Usually I say don't trade a car in for the same model, as it won't feel different or new. In this case, however, there are a lot of improvements that make upgrading worthwhile. The suspension and steering have been improved, and the 3.6 lets you have your cake and eat it too, with 55 more HP and significantly improved gas mileage. With the 3.5 V6, you didn't really get much better mileage than the 5.7 in the R/T.
I was in a similar position. I had a 2009 Challenger R/T and normally wouldn't want to trade for another Challenger. In stock form, the 6.1 didn't run any stronger below 4000 rpm and was a lot thirstier. Then along comes the significant suspension improvements (performance wise), improved steering and the 6.4 with lots more power and improved fuel economy. When a good deal came along, I jumped on it and have no regrets.
So bottom line is think you will like the improved handling & performance enough that if you can get a good deal on a trade, it will be worth it.
