My take is that it depends on the Campaign being run (in which case the real difference is the HP and the looks), but in general I find that it is...
1. Orcs are more like Cattle (at least initially, NOT the racial identifiers some try to use in this thread, though perhaps it is true in regards to 3e to 5e. The connection to derogatory racial ideas in 3e and 5e are very problematic, but that's not the initial idea of Orcs) or demonspawn (from the ideas of being either bred or spawned from evil from the Tolkien LotR trilogy, which is where I feel the Orc monster ideas originally came from).
Orcs appear like rabbits, and band together like many other monsters or creatures into tribes and groups. However, because they are more like Cattle or herd animals, they are very easy for Villains to take control of and use as their minions. Orcs are intially rather chaotic in nature, and tend to do things that many others would find vile (or evil), but are easily sway-able and thus many Villains try to get them for armies as fodder.
Having them come at you is like a stampede of cattle (which is EXTREMELY dangerous if you've ever been in that situation), or the untamed bull in the field (Bulls can also be VERY dangerous, and very aggressive) on a more individual arena.
2. Hobgoblins are more like Army Ants. Very militant in many ways, but also very driven to do their basic thing. Unfortunately, that thing involves conquest many times. They too can be utilized by others, but it is normally more of a top down thing where the villain controls the leaders rather than like the Shepard or cowboy controlling the herd/flock.
As an army they can be a persistent force of nature, consuming everything in their path.
3. In Pathfinder 1e Orcs vary greatly between each other. In general, the differences as put in the Bestiary state
the primary difference between orcs and the civilized humanoids is their attitude. As a culture, orcs are violent and aggressive, with the strongest ruling the rest through fear and brutality.
Meanwhile Hobgoblins are
...militaristic and fecund, a combination that makes them quite dangerous in some regions....
....Of all the goblinoid races, the hobgoblin is by far the most civilized
I think this actually reflects in many ways the more traditional ways of looking at Orcs and Hobgoblins from the past than more recent ideas about them.