FWIW, choose the design you like best for your application, but do not mistakenly believe some features have some substantial impact on performance.
For example - gusseting, it may not make any real difference in strength. If a grapple tine is 4 inches long and the gusset is 1/4 inch, the tine is now about 7% more resistant to deflection at the tip. Is 7% meaningful? Additionally due to the extra welding of the gusset, the tine's metal may have been weakened and/or made more brittle.
For example - serrations/teeth, there are advantages and disadvantages. My grapple is smooth, and in three years I have never had an issue with securely gripping material - compression does nearly all of the work. Serrations might offer some minor improvement in grip, but they also present some problems. Serrated jaws can make releasing material more difficult as small branches, vines and other such things can get caught in the serrations. Picking up large rocks can also be more difficult with serrations as the rock can bind on the teeth preventing the jaws from fully closing. Many will say serrations (really just teeth with no sharp edge in between like a knife) help with cutting roots. Do they and by how much? Roots tend to be snapped/torn by grapples by pressure - not cut by a sharp edge. The roots I have ripped out tend to snap or pull from the soil well clear of the actual point of contact with the grapple.