What model Sadowsky Metro are you looking at? If it is a Jazz or PJ I have no idea where you teacher is coming from. Nether of those would be considered a one trick pony and both would be highly versatile instruments. Even a Sadowsky Modern can be versatile. My Sadowsky Masterbuilt Modern is my main player and one of my all time favorite instruments. Sadowsky's sit in the mix incredibly well.
I'm not a fan of the 35" scale on the MTD's but that is certainly personal preference. I am also not a fan of the necks on the Sadowsky MetroExpress either. Very heavy and chunky feeling and really nothing like a Sadowsky Metroline, Masterbuilt or NYC in feel.
So tough choice. I wish the MetroExpress team would shake up their neck builds/profile to be like the Metroline. Would make the Sadowsky an easy win for me.
Another instrument to look at would be the new Ibanez Mode Jazz basses. Those necks feel much better (to me anyway) than either the Sadowsky MetroExpress or the MTD 35" scale Kingston. The price is right in there too.