In runner motors are stonger, but still subject to bent shafts.  Most electrics use pretty small shafts like 5 mm or so.  Some people use a prop driver set close to a firewall so the shaft can't bend to far.

Out runner motors are a lot more fragile.  If you mount it on the stator base the rotating can is exposed and can easily get knocked cock-eyed.  You can mount it on the back side of a firewall with the rear shaft sticking through.  Then the shaft can be protected like an inrunner, with a close fitting prop driver.  You might even mount a bearing assembly on the can so both ends of the shaft are supported.

But then, if you wreck one, it's only an electric motor, not like wrecking an OS or a Rossi, or a Nelson.

Lee Liddle has been using electric motors on his RC Combat planes for several years.  He is using various Turnigy brand outrunners and has been having great success.  He occasionally bends a shaft on a "dirt nap" but they are so cheap, that it really doesn't matter.

I saw an 18-oz. high-zoot LiPo get flung out of a stunt plane once.  It hit the ground and nothing happened.  These things do not spew fire as advertised.  They have no place in combat. 

That, too, has been a disappointment: four (4) accidents in one year, no fire.  The Prius is smaller than it looks, hence people think it's farther away than it is. 

Years ago my mother picked up my stuff and put in a box to go to the basement. She set the box of batteries, and steel wool... on the stairs for me to find, it wasn't there long when I found it smoldering in time to pitch it out the back door.