Pros:
Better sustain. Trynd has to build fury, then use it to heal.
A stun.
Variable build paths, full ap, full ad, bruiser, splitpush, teamfighter, etc
Better team fighter than Trynd due to stun
Variable skill order.
You can still be useful if behind due to stun.
Cons:
Mana-dependent. You almost always need at least one mana item
Lower DPS compared to Trynd.
No dash for escapes, but high movespeed is usually sufficient.
No ultimate, so it can harder to fight some champions.
No real waveclear without getting Phoenix or a hydra item
Pros:
Innate crit and synergy with crit.
Pretty decent waveclear w/items & E.
Innate sustain.
Ult. Self-explanatory.
Good chase potential with slow and E.
Better duelist of the two.
No mana to gate him.
Cons:
All you can do is split. Team fights are usually fruitless.
No variable build path. You almost always want just full glass cannon.
Falling behind means you're meaningless in every sense other than a distraction.
Very predictable. You know what to expect from a Trynd in almost any scenario.
Hope that helps. It's up to you who you take, but that's how I'd evaluate it.