The "E" machines have slight less lift capacity than the R's do, hence my recomandaion. I think 55" is good for your sized machine, but weight is a bigger consideration.
If the primary purpose is bush, you can go a bit wider which will be a bit heavier as well. When it comes to moving heavier stuff like logs, you'll just have to reduce the size of the load a bit.
If the primary use will be logs, the lower the weight of the grapple will increase your productivity.
Think of it like bucket capacity. If you move a lot of loose debris a larger bucket works. The few times you need to move gravel, you just have to take smaller loads.
Strong grapples that are lighter in weight require a bit move engineering and higher grades of steel so expect to see that reflected in the price.