I collected these stats from other discussions
Here are my favourites:

Set bonus
Pros:
+15% afterburn duration
-75% airblast cost.
+200% max primary ammo on wearer
+20% move speed on wearer

Cons:
-25 health
-25% secondary damage penalty
-25% slower weapon switch

Afterburner
Pros:
-100% self-damage on Airblast Jumps
+25% Afterburn Damage and Duration
+Recoil On Airblast (Can Airblast Jump)
+40% stonger airblast

Cons:
+20-30% Faster Ammo Consumption
+100% Airblast Cost
-30% Damage

Spitfire
Pros:
Like rockets, Projectiles fly straight, without an arc.
+ Projectiles explode on impact.
Crits while airborne

Cons:
-15% Projectile Speed.
-20% reload speed
-10% Max. ammo

SHARE YOUR STATS AND OPINIONS

Thanks to:SilentStormCZ, (ESP)Dr.Ciprés ( ͡° ͜ʖ ͡ , vladax94, Gamester, people who discourage W+M1, Reserve Shooter Ripoffs and Pyro headshots, Kaa Kensington, PEACE_ and others