When you convert a v-grind factory bevel like those on the rats, what you are actually doing is knocking the bevels off and smoothing out the transition between the coating and the blade. Often times, you don't actually alter the very edge of the knife except that it becomes more polished than how it is supplied at the factory.
Since we are talking about a modded knife in the above fashion it doesn't make much sense to spew out all the common reasons of why convex may be different than a V-grind. For example, the robustness argument often stated for an advantage of the convex edge isn't applicable here because you've actually removed metal by knocking those sholders back. Thus a convex converted rat is arguably a little bit less tough than the supplied V-grind version.
Having done said mod to all of my rats I can say that my perception is that the knife slices much better. By slicing, I'm talking about cutting into a material past the bevel. This isn't the same as a paper push cut or a hair shaving test which essentially just measures the sharpness of the very edge. You won't find any difference in the performance there.
Where you do find a difference is for example cutting through a thick piece of meat, slicing veggies and splitting wood as in the case of batoning. In the later cases, the lack of a bevel transition and the smoothing out of the coating reduce friction through the slice.
Another advantage of convex is in how you sharpen them. Simply stropping with a piece of sandpaper on some soft leather or a mousepad and then proceeding to leather only will let you field sharpen a blade anywhere without need for bringing out ceramic rods or stones. I don't generally pull out that point because, personally, I rarely find need to sharpen my blades in the field. However, if you are processing a deer, then being able to bring your edge back to sharpness by just stropping it on the back side of your belt could be an advantage. Some folks I know even rub green sharpening compound into a portion of the back side of their belt for this purpose. This leaves green compound on your pants of course. The guys I know who do this just use BDU's or field pants so they don't care about staining between the belt loops. They just like the versatility of a belt that holds their pants and sharpens their blade.
