The 977L is a great machine for demo, but nothing compared to the demo capability of the larger 983 and even better 983B. The 983B was the demo loader of choice in New York City up through most of the 1980's, and even into the early '90's.
Heavy and brutally powerful, with a push stick, this machine couldn't be beat. In fact, we had a total of four of them come in to our yard two years ago (ranged in age from 1970 to 1982) as "trade-ins" on the purchase of a new Komatsu PC1250LC-7 to be used by a NY City demo contractor. The 983's, even with the hours and rough body work they had, were gone as fast as they came in. They were, and sometimes still are very highly regarded as a demolition machine.
The 977L was lighter and had less power, but was just as bulletproof (even moreso) than the 983's. 977L's were very popular in the earthmoving segment due to their bucket capacity vs. ease of moving.
They were both very good machines. You can't go wrong with either one if you're looking for a big, powerful crawler loader.
Tony