I've made a 50 minute connection in MAD (TLV - MAD - ORD). It was IB to IB, all in 4S, and fortunately TLV-MAD landed early, albeit at a stand with a bus to terminal. It's doable, but there is no margin for any delays. It depends on your situation, but I'd try the 55 min connection as long as there is a later flight as a fall-back if you miss it.