In The Battle Of The Pelennor Fields the orcs of Mordor appear to fight on after the Sun shines (a great wind blew, and the rain went North). The hosts of Mordor, which I would say included orcs (orcs that are said, after Aragorn is revealed, to have hated the Sunlight), were actually heartened by the Black Sails.

Éomer's words include singing in the Sun as he prepared to face Mordor, and then Aragorn and Company are revealed and a dread falls upon the enemy. These orcs do not like the Sun but appear quite ready to battle on when thinking that the ships contained enemies of the West.

Orcs don't like the Sun. Perhaps even Saruman's Isengarders would prefer darkness if given the choice, but in any case the evidence appears to imply that the Isengarders are arguably better at enduring it than others orcs met in the tale, though even they are possibly matched by a few 'larger, bolder' Northerners.

When running with Merry and Pippin, the Mordorians run 'hour after hour' under the Sun without complaint (granted the Winter Sun if I remember correctly, but still), and even when they drop back at one point (compared to the Isengarders), the text makes it clear that 'the writer of the tale' cannot know (or tell) the exact reason why, and the writer gives two options for the reader to entertain.

I haven't looked at the Silmarillion texts (yet) concerning the matter, but in general I'm not sure the suggestion from certain descriptions in The Hobbit necessarily speaks for all orcs in the legendarium.

So please help me out (those who care enough!): did Tolkien sustain the idea well enough in The Silmarillion? and elsewhere (Unfinished Tales). It is a rather nice enough idea I think, and Treebeard certainly seems to think it odd for orcs to easily endure the Sunlight...

... but in my opinion, so far at least, although this was a concern for JRRT, the matter doesn't seem so set in stone (troll-pun intented) as it might appear.