B670 Backhoe Bucket test

I had always used the 10" bucket on my B670, lots of hard soil & rocks here, but I recently put my 14" bucket on to try it out. I used it to clear the ditch at the end of a culvert, mainly sediment washed in- sand, gravel, clay, & some rocks, all hard packed. It did OK, and the extra capacity was nice when removing spoil from the hole, but it was obvious that it would not perform well in the typical hard packed rocky soil I usually dig in. The extra 4" width & one more tooth are just too much to ask the little hoe to drive into the hard ground & rocks. If I ever move somewhere with soft, loamy soil, I'll probably never use the small bucket again, but here, it's gotta be the narrow one. Incidentally, my manual calls them a 9" & 13" bucket, which is the actual width of the bucket without the side cutting edges. They dig a 10" & 14" width trench respectively, and the manual claims .63 cu ft & 1.00 cu ft heaped, respectively.
!st pic shows the two buckets; 2nd, the wide bucket clearing the culvert; 3rd & 4th, the narrow bucket & rocky crap I normally dig in.

The BH77 looks a lot beefier than the B670, looks like it would handle the wider buckets easily.