tj,
Like you I have a P3S and wanted something more portable to travel/hike with. In this regard, the Spark is an excellent choice. One thing often overlooked with the Spark, is that it is the only DJI drone that can be docked and charged on the go via the Portable Charging Station. There are 3rd party solutions but they are not as convenient as the Charging Station. For me this has been a major plus with the Spark. In the summer, the family and I do a lot of camping and often we are in a location without access to power for some time so the ability to charge the Spark on the go is important. Also, it is handy when hiking as well.
Instead of trading, your P3S why not keep it as a backup in case something happens with your new drone. I find that I still use my P3S when I don't need portability or a quick launch. I used to have a hard case for my P3S but that even reduced the portability even more, so now I use a backpack and other than freezing my hands off screwing on/off props, I can even take it hiking.
Good Luck with your decision.
Chris