Filet mignon or New York strip, medium rare. I also like a prime rib and rib-eye.
Frankly, when eating out I usually judge by what's the most expensive item on a restaurant menu, plus I'll ask the server. Obviously they could be motivated to steer me to the most expensive thing, to increase their tip.
But I can usually discern knowledge from personal interest, and may choose a less expensive cut, if I feel in the mood for it, and also based on what I think my appetite can handle.
I know take-home is common now, and I do it, but rarely are leftovers as good at home the second time around, steak especially. Plus we tend to know the servers at our favorite places, and they understand it's not in their best long-term interest to advise us according to their tip that night.