I get more kills as a stormboy (level 4, nearly no stormboy specific gear, i don't have the burny choppa for instance) than as a raptor (level 5, nearly all boxes unlocked, i have and use the necrotic chainsword for instance). The reasons why I kill more as a stormboy are:
1. Extra resistance, due to shitty ork animations and thus hits missing me (I presume, i'm not really that sure)
2. The pistol with the long clip, the one most ppl use, the dakka slugga i think it's called, is much better than any chaos pistol

I do think though that slower fast hits may, depending on playstyle, make some players, unlike me, better with raptor than with stormboy.
What is certain is that the "larger hitbox issue" is less of a problem with stormboy than with other ork classes, but that is rather obvious.
I would need to get that burny choppa ta reaaaaly stomp da umy whiny grots !!! (sorry) to really be able to compare raptor and stormboy, cause both the burny (at least i'd imagine) and the necrotic (that i am sure of) really make a differenceas you can fly off and let the poison/fire finish the job, as well as cause panick to the yougest players out there. I do know that i have died a lot to the f...ing burny choppa (in French we call it The Choppa Burné)

For the first one, the hitbox isn't as much of an issue since your not exposing yourself to fire as much due to maneuverability, when they see you, you will die. If it's a tactical with a bolter who Dbash stuns then backpedals to shoot you- I've survived that as a raptor, but not as a stormboy. mostly due to how easy the head is to hit vs Orks at point blank range.

Second, Muh Bolt Pistol.

For the latter, be aware than the Burning Choppa doesn't apply burn on a Dbash the same way the necrotic chainsword applies poison in that situation. I've been poinsoned by it during clangs too, but not burnt with the burning choppa on a clang. (LSM Apoth Narths also apply poison on Dbashes too, because apparently even their feet are poison.) I'm not entirely sure which weapon in this situation is bugged. You'd think in fairness it would apply to the Burning Choppa too, but may have something to do with it being poison and fire damage.

I think it is a latency problem with servers and fast weapons. The narth and chainsword are fast enough to cause ghost hits despite last second clangs but the choppas aren't. If the burny choppa swing animation was sped up a little I bet it would also do the same thing.

My biggest problem with orks is - and has been since they were added - the shoulderpads.

Ork shoulderpads are just plain awful looking, low poly, simple models. The contrast with the exquisitely detailed muscle underneath just looks horrible and as a result im rolling with no left shoulder and the leather right shoulder (just because it replaces the model with a less-bad one) whenever possible.