Personally I would use the one you already own, It's not a huge difference in weight or HP, If it proves to not be up to the task....then you could make a change.
That’s what I have been leaning towards, just a little nervous to tear up one that new running it through the woods. I would be miles ahead on money if it worked though.I am Really curious if anyone out there has ran them side by side to see what the differences in performance really is.
I can't help you there, that's a decision you'll need to make after weighing all your options, I will say this...the picture you see to the left of this post is my D6C, it's old and its slow....it's hot in the summer and I'm sure it's cold in the winter although I don't use it in the winter. It'll do a lot of work...and you'll get a workout running it. I have operated hydro dozers and they are a different animal. I don't believe the D's are a lot different than my C. Others may have a different story to tell.