Top edge is sharpened on the #8...not the #5. Thumb notches are standard on the #5 and additional cost on the #8. Some states do not allow TB (top bevel sharpened) hence the #5 would get the nod. #8 is upswept on the blade shape and then "drops" to the straight point. #5 is dead-ass straight all the way.
Aside note: "I" prefer the T&B for game work because it cuts around the anas and does a much better (surgical) job of beginning the gutting process. I prefer the #5 for camp chores as you can only get "cut" from one side...should you have a "slip..fall..or a slip-n-fall"!
Capt. Chris