Everyone sings the praises of a King 3B trombone (along with Conn 6H trombones and other similarly-sized instruments that play well), but none of those people will bring something like that to rehearsals, or dare to try using something like that to play Mahler. If they would just spend some serious time with instruments like that (ok...in the same way that "if tuba players would just spend more serious time with their F tubas"), I believe orchestral principal trombone players would become more comfortable/secure with instruments like that, and wouldn't balk at using them - when really good instruments in that size range have so much potential to make their jobs so much easier. "Because that's not how it's done" is not a good reason to not consider/explore the possibilities of doing anything in particular, or is it?
Additionally, most of this could be applied to quintet trombone playing, though I sort of think that the ideal quintet trombone is probably one of those that's only about 20/1000ths smaller in bore, and with those 8-1/4 in bells, because the quintet trombonist is expected to play in such a wide frequency range.
To me, the .547" bore trombones with f attachments are ideal for orchestral >second< trombone playing...
... I also am of the opinion that a whole row of trombones of the .547" size in a wind band is a bunch of trombones that are too large.
Tuba players are somewhat this way, but I find trombone players - on average - to be particularly group-thinking...ie. "Were I to begin using a .500" or .508" bore trombone to play my 1st trombone parts most of the time, it would get around to other players in town and other players in other orchestras in other cities, and what would they think of me?"
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I would argue that it is not. There's only one tuba position in symphony orchestras (not three high/middle/low tuba parts - and thank goodness for that), and I use all sorts of tubas that I bring along to play different pieces of music. I believe that I vary my equipment as much as most any working tuba player - probably more than most all, and don't mind dragging along two or even three instruments - if those will play particular pieces best - in my judgment- and deliver the most musical effect. Pretty much, I've decided that my very large compensating euphonium is the biggest thing that I need to use to play serpent and ophicleide parts which have been assigned to tuba players (with a confident compensating range being important), F tuba is appropriate for way more pieces than many American tuba players would agree (I recently used mine to play the entirety of Mahler 1, and not just for the humorous solo in the slow movement), I use my really large tuba to achieve the types of effects that composers/arrangers write that obviously have that type of sound in mind, and I use my F cimbasso that I built - probably 1,000% - 10,000% more often than other players who own similar instruments - to play particular pieces of music (whereby an arranger seemingly/obviously reluctantly assigned a fourth trombone part to the tuba player, because that's who they knew would be there to play it)....but bloke, look at your own huge tuba... Is this the pot calling the kettle black?
Trombone joke, sorry.
On trombone, bore is mostly about how much air you can put through the horn before it starts getting edgy. This is why symphony players play on big horns - they want a lot of volume with no edge (I believe this has changed over time, we used to think some edge was ok in some works). This is also why playing alto in a big orchestra can be tricky - those small bores can edge out pretty early. This is also why big band players should play smaller horns - you want a little cutting edge especially when the top part gets loud (you find a surprising number of big band players who insist on playing 547 for lead book 
). In pop music you should avoid big bores because the large bore just makes a lot of mud which is unpleasant to listen to and makes everything else hard to hear, while the small bore will get some edge and be heard.
