Arial is just permafly and more dex. Parry may be worse, but in theory at full stats an arial should have better defenses than a human.

Felar is for the hp, the gear, and the fact that backfist (and spears, and staffs) are useful. Heat vuln is way easier to cover than arial's lightning vuln. Both have water so that's a wash. When I say "for the gear" I'm mostly thinking of front/rear extensions. Other stuff is good too, but not necessarily a game changer.

Human gets you no vulns and a better range. Though, if you plan to play the character for a long time (and not level sit) then this is less important.

If you plan to go maran: Felar looks a little better and arial looks worse.
If you plan to go battle: Arial looks better.