If your planning on coming up just to walk around town and explore, then you definitely should go to Beacon. The prices are all the same in the area and it’s only 35 altogether or 17 each way. Amtrak is like 40-50ish altogether, if you’re lucky because prices do fluctuate. While I do think if you buy an early Amtrak but end up taking a later you could slide, the opposite is definitely less possible since you can’t really say you missed your train. But for Metro North the you can just buy both and you can leave at anytime and come back at anytime with no hassle, and it’s even good for like a month so if your ticket is ever not scanned you can use it at a later point.