Best blade length and shape for field dressing is a clip pointed, fairly narrow, blade at least 4" long, fixed (not folding- those are a PITA to clean blood out of) blade ..... sturdy enough to whack through the pelvic bone with the back of a hatchet.
Mine's a "Utica Sportsman", available on E-bay for next to nothing. I got mine for less than that out out of G-pa's kitchen junk drawer. I've been gutting deer with it nearly every year that I was not deployed to BFE since I was about 15.
http://www.ebay.com/itm/UTICA-Sports...item48647c7a61
For skinning, I like a wide knife with a lot of belly. I could not find what i wanted, so I made my own from a 10" heavy duty miter saw blade.