Can you please tell me What is the biggest difference in these 2 wood shaft materials besides "toughness "? Is there a benefit from one to another?

Doug fir will also tend run a little heavier than POC.  However, the heavier cedar at a given spine will weigh as much as the lighter or mid-weight Doug Fir in the same spine.  The difference in hardness between growth rings is a little more pronounced in Doug Fir, making it a little harder to sharpen cleanly with pencil sharpener nock and point type taper tools. Doug fir's extra physical weight may or may not be an advantage, depending on intended use.  Its greater durability is a noticeable advantage, though I have come across some Doug fir that was brittle and prone to breaking.  I've never experienced brittle POC. They both take stain well;  Doug fir is a bit more showy.  They're both excellent arrow woods, IMO. 

POC smells better    I liked the tapered Doug Fir more than parallel shafts back when I was making my own arrows. Both being wood, I broke a lot of both but fir was a bit sturdier than POC.

I was in the packaging business and had a customer who made cedar filled dog beds " Cedar Sack " they gave me a BIG jug of Cedar oil and every once in a while I'll spray a bit in the man cave. Like a time machine taking me back to bygone days.     

When I get Doug fir shafting from Surewood,  they are amazingly straight.   Like I've never experienced with cedar,  and I've messed with cedar a ton.  Yes you can get any wonky cedars straight with some tweaking...... but I feel you practically never have to with Surewood's Doug fir shafting.   I'm gonna say they are substantially tougher than cedar too,  not just a little tougher..... a lot tougher!  If you jam a few on top of each other into the target, they fair very well compared to cedar.  They don't smear and crease the same way cedar does.   There will be the slight deformations,  almost never the type of gouging that happens with cedar. 
They are definitely generally heavier if that is of value to you. To me,  the only thing cedar has on fir is the smell..... which I love..... but accounting for all pros/cons between the 2,  I'm spending my money on the Doug fir.

For a hunting shaft, Doug fir is typically a bit heavier and sturdier whence compared to typical POC shafts.  I prefer Surewood Doug fir shafts.

My personal experience is that the quality of Douglass Fir I get from Surewood is consistently excellent. I have not found that to be the case with Cedar and I've tried a few sources.

Thank you for all your input

Ive never shot cedar except for maybe old arrows when I was a kid. Seems like sources for good cedar arrows can be hard to find, where as with fir you just get them from surewood with no worries.

I really like the tapered POC shafts I get from Wapiti Archery.

That said, I have received excellent Douglas Fir shafting from Surewood in the past.

Personally I like both, made up both, lost both, broke both. Right now I am making up a couple dozen, one cedar, one fir for "shooting ".

As mentioned by several, the Doug Fir is consistently a bit heavier.  I shoot tapered arrows in both, like both, but DF is heavier to allow good arrow weight with my heavy bows.
 

I've used both cedar and doug fir. I like both of them although I make way more cedar do to the fact I have a stash of premium cedar. And while fir can be typically heavier I not into that due to me having to drop too much draw weight. I like aa arrow that's a compromise between weight and trajectory.

I like both, but have a preference for POC shafts built by ACME. They stand out with straight tight grain, and will make a superb matched arrow.