Does the school offer you any financial incentive to stay with them?
How much more do they charge for the Tecnam then for the 152?
Did they offer you to finish on the Tecnam for the "old" 152 price?
I have about 10 hrs in a Tecnam, somewhat enjoyable but "jittery" compared to the slo-mo 152.
You will definitely need some transition time so it might be a wash depending on what they charge for the Tecnam vs the gold plated 152 the other place is using.
Example; Tecnam is 100 and the 152 is 125.
You need 5 hrs in the Tecnam to transition and become equally proficient as you were in the 152.
Cost is 500.
You move to the other school and need another 20 hrs to finish your PPL, the extra cost is now a wash.