I think the logistics of a naval campaign are substantially more complex, and on those grounds alone I would argue in favor of the Admiral. Ships are technology that must be maintained and understood by the men who fight them before they can be of any use in battle.

A soldier without a gun or sword can still pick up a rock or stick, or even use his bare hands, and be at least minimally effective. If someone blows a hole in your tank, or shoots your horse out from under you, you may still fight effectively on foot without much trouble. A sailor without a ship is shark bait, he serves no purpose but to force other ships and other sailors to attempt to rescue him.

Deep water is inherently hostile to human existence in a way that even the most inhospitable ground conditions are not. You will never encounter drinkable water just casually in your path as a sailor, while soldiers have historically carried very little of the stuff precisely because more than a few days rarely passed without finding some.

A soldier seperated from his unit can still fight and survive in the wild while trying to link back up. A sailor seperated from his unit, even if he is in the relative safety of a life boat, cannot fight and cannot survive on his own for any significant length of time.

An Admiral must account for all of these factors on top of keeping his technology, even if it's as simple as a straight mast, a well made sail, or a correctly braced and placed outrigger, operational in an environment where none of it can be replaced.

P.S. Note that I left out the complications of wind power and accurate navigation absent landmarks because those wouldn't in any way apply to a modern navy, but for 90% of the recorded history of warfare they were significant difficulties that land armies simply didn't face.