what are the differences between d3 d3b and d3c

I have the opportunity to buy one and of the 3 there are going to be pros and cons but they are all priced the same...I'm a first timer but worked a new 450 john deere and familiar with a 455g JD loader. Know nothing of cat but know about undercarriage enough to stay out of trouble. Pics I looked at d3c has better rops system but has 7900 hours. D3 has scary looking rops/sunshade and only 1900 hrs Both have 6 way blades. I don't plan on rolling over.