Depends on the situation. If we can and need to move the ship then I trust my crew, no point captain tanking if the guns cannot shoot (unless it is a capture point map). If we cannot move the ship the way we need to or we need the front gun rebuilt or we don't need to move the ship then I will jump down, often letting the engineer know to prioritize something else (typically the front gun if in arc and down or the engines so when I'm back on the helm I can be useful again). I've even jumped on side guns before when in a 2v1 because the engines were too damaged to use shine, the engineers were busy, the front gun had arc on one enemy and there was another on a left carronade. Set the controls to 'get the heck out of dodge', jump down and balloon pop so you can disengage. Point is sometimes, but rarely, giving in to that urge is the right tactical decision.
If none of this applies then I trust my crew, even if they are new. I'd rather let my crew learn than try (and fail) to compensate on my own. So long as they don't repeatedly make the same mistake over and over I don't care if folks mess up on our ship. The way to make me grumpy is to not listen, not to do things badly. And a pilot with a spanner and some random ammo type cannot compensate for an inexperienced engineer or gunner anyway.
For me the worst temptation on a fish is to take one when it isn't necessarily appropriate because of the command advantages. If your ally is communicative but inexperienced and your gunner good there are few ships which free you up to help your ally like a lumberfish, especially against good opposition. As you say the pilot has a good field of view, has limited utility to the engineers (occasional balloon rebuilds and very occasional hull rebuilds), good view of your crew and an easy to maintain arc on the main gun. It is also pretty fast allowing you to pick ranges and positioning, all things you can use to compensate for your allies inexperience so long as they approximately implement a plan with you. Since it is an easy ship to do all these things in you can devote time to talking to your ally and helping them if they run into problems.
The temptation part comes in when you bring a goldfish in the hope that your ally communicates because the opposition is strong and you end up without any raw killing power. Your ally doesn't communicate so you've freed up pilot resources for little more than jabbering frustrated into a mic, they don't know what they are doing so they don't kill anything and they die, repeatedly. You just cannot kill the enemy as fast as your ally dies. None of the standard fish builds are fast killers, and the best for this kind of communicative role (the lumberfish) is the slowest of the bunch. Closest is a hwachafish but even it has a three step process (disable, strip, kill) for killing versus most DPS ships two step (strip, kill), and it is more demanding on the pilot as you swing back and forth to the gat, you cannot be baby sitting your ally while doing that.
I've made this mistake on a couple of occasions now where I've known after the fact better pilots and captains would bring say a brawling spire. Sure you make the match more dependent on the skill of you and your crew, but polite captains who appreciate their crew and try to provide them fun matches get good crews even if they are mediocre pilots. It works in part because your ally acts as a tempting distraction while you do your thing. The enemy knows a frontal assault on you will be hard so the try to focus down your ally and you just kill one of them with the spires massive firepower.
