Maybe the sap will be more maliable and can take any shape and get harder than rubber. Would also grant logia like abilities. I think the more important part is if the resin is from the Adam tree which is the strongest tree in one piece or if it was made from the original devil fruit tree. I think the back story of luffys devil fruit is what will make it important not necessarily the power up. Maybe it's just that it will inspire people to ride against the world government when they learn the legend of joy boy and Nika are true. Obviously the fruit isn't all powerful because in the end Joyboy got defeated 800 years ago even with Zunesha.
A youtuber brought up some combat applications for sap that I actually thought were cool. If Luffy could produce/make more of it we could see sap weapons or even sap clones (that might be too similar to Naruto though). In addition to sap changing shape easier. Also, what about sap's stickiness? Anyway, I'm just going to leave it to Oda. I'm sure he thought this out.