technically i would say that fire wolf has better horizontal and vertical reach in terms of distance, the only problem with this move is the extensive amount of start up lag it has and the lack of priority it holds, a good opponent can see it coming and hit you out of it very easily putting you in a terrible position.
wolf flash on the other hand has just as bad of priority i believe but its angled and its so demented that its considerably tougher to punish (though still pretty easy) flash also has the benefit of spiking or doing a decent amount of damage whereas fire wolf can still be stop by certain moves (marths up-b) even after you've hit them
So basically, try to never recover low, you're pretty much dead if that happens due to a edge hog, save your 2nd jump for the last moment and if you have the space or time use fire wolf to recover, if not then wolf flash is your best bet.
Besides his two recoveries, I'd say that fsmash leaves you the most vulnerable if you miss the hit, which makes for a double edged sword, good punisher but easily punished. if you don't auto cancel a fair (by DI'ing the move as you use it) it has a lot of lag as well once you land.
The grab or the chaingrab? the chain grab you can't get out of unless the D3 messes it up. The grab itself can (if you're at a lower %) its just as simple as mashing the crap outta your controller, there's a technique to it but i dunno know it, i just mash away. Hope that helped :D