Jadavpur University is definitely better than IEM. It is ahead In terms of placement, academics, and research. In the 2021 NIRF Rankings, JU ranked 17th for B.Tech. It has outranked a few of the IITs. Whereas, IEM is ranked 191 for B.Tech by NIRF 2021.
In the 2021 placement drive, the placement average for IEM was around 75%. For JU, the placement rate was 100% while the average CTC offered was 19 LPA.
If you have a specific branch in mind you can go for IEM. Otherwise, choosing JU will be better. The preference of choice should be like the following.
JU (CSE/ECE/ME/EE/Chemical/IEE)> IEM CSE> JU (Civil/Production)> All branches of IEM> Rest of the branches of JU.