Your favorite unit...

The Priest is very strong! Not only is he tough as nails, but he also deals a lot of damage – this wall is just ridiculous, and when he starts shooting at multiple targets at once, you're in trouble. But the thing is, he often doesn't even need to shoot. Dwarves don't hit very hard (up to level 7), but they are very durable, so battles often take place on their side of the battlefield...

Added 2 minutes later
The Jarl is frankly weak in terms of damage, but he hits many targets at once and is very fast. During a siege, you can basically throw them with an energy rune right behind the fortress wall for an attack – that's also a good plus.