Well, tbh, if it's simply a choice of which key to map to the currently-Caps Lock key then Escape should be the winner even if exiling Caps Lock to the Touch Bar would cause significant annoyance to some heavy users.
However, while users are mostly just faced with perhaps-hard choices about how to remap the given keys, the keyboard manufacturer and integrator Apple had many other options. Caps Lock is currently 2U wide on both ISO and ANSI layouts https://i.ytimg.com/vi/3tJagPz-xIw/maxresdefault.jpg , so it could fairly comfortably be split into a 1U Esc and Caps Lock. You could even give Escape the outside position: that's not a big reach, just the mirror-image of the ISO English # key and more convenient than Esc's existing position in both ANSI and ISO, and there's an arguable case for not putting Esc on too much of a hair-trigger position near the home row anyway. Alternatively you could carve a 1U key out from the right of the right Shift, which is pretty uselessly overlong on both ISO and ANSI.
However, while users are mostly just faced with perhaps-hard choices about how to remap the given keys, the keyboard manufacturer and integrator Apple had many other options. Caps Lock is currently 2U wide on both ISO and ANSI layouts https://i.ytimg.com/vi/3tJagPz-xIw/maxresdefault.jpg , so it could fairly comfortably be split into a 1U Esc and Caps Lock. You could even give Escape the outside position: that's not a big reach, just the mirror-image of the ISO English # key and more convenient than Esc's existing position in both ANSI and ISO, and there's an arguable case for not putting Esc on too much of a hair-trigger position near the home row anyway. Alternatively you could carve a 1U key out from the right of the right Shift, which is pretty uselessly overlong on both ISO and ANSI.