I go back and forth on this so often, to the point where I'd probably be willing to flip a coin to decide.

Head first has the joy of consumption being incredibly visceral. The prey is immediately enveloped in slimy flesh, darkness, and all of the noises associated with getting swallowed. It's an overload of sensations that can't be escaped, they're immediately trapped and in it for the long haul, with nothing to look forward to but the feeling of fresh air on their legs slowly disappear with each swallow.

Then you have feet first, the option with a higher chance of escape, owing to the prey's ability to move their arms and kick their legs. As far as I'm concerned this is the option for the most willing of prey to test just how willing they actually are. If they allow themselves to be slowly swallowed feet first and don't put up a fight, they deserve what's coming to them once they're inside. Sure, you lack the immediate visceral consumption experience, but you get more time to consider the consequences of what's happening, as well as the gradual introduction of your legs and body into your predator's guts with all of the associated feelings.
Bonus points: For better or worse, you save the full digestive experience for after the final swallows. It might not be clear how nasty it is inside a stomach until you're fully inside, but you let yourself get to this point so...

Guh, I love both so much, but I also love games of chance deciding my fate so...pred flips a coin?