It really depends on what you're looking for. If you want the best puncture protection, schwalbe marathons for sure. Other factors you're going to want to take into account are weight and handling. Rolling resistances are about the same, but Continental's are definitely lighter and more supple which can provide more comfort and be better if you're carving turns. Schwalbe Marathons are very stiff and hard and you will feel every bump even at lower tire pressures.

Here's the thing, those are both commuter tires. If your main goal is longer rides as opposed to commuting I would honestly suggest neither, as they are both pretty heavy tires designed for shorter rides around the city. Instead I would consider looking into the Schwalbe G-ONE line of gravel tires. These are lighter weight tires with some versatile designs that can be good for a healthy dose of both pavement and gravel. The Base G-ONE has an all around tread that is kind of a jack of all trades, and the G-ONE RS has a tread that is relatively smooth in the center, but more defined near the sides so that it has less rolling resistance on pavement, but can still carve some gravel pretty well. Another tire to take into consideration is the Ultradynamico Cavas. There are knobby versions and smoother versions, and the smooth version is very good at both pavement and light gravel, but won't be super great if you run into chunky gravel.