That depends tallcorn. The 3500 has 24,000 more btu than the baby, and with them both at idle, the 3500's 75lb hopper (of corn), will last half the time more than the baby's 50lb. However, with both stoves running wide open, the baby has a little more hopper per btu than the 3500. I never had to fill it more than twice a day. The ashpan is smaller but being just a clinker stove, it can go days before dumping.
As far as the baby heating 852 sq ft., if it's well insulated, it should. The house I sold was newer 2 story 2100 sq ft and I figured the baby heated at least half the house. With a few days with severe wind chills and zero temps, the baby was wide open and even lost a couple degrees inside. On milder days in the spring and fall, it heated the whole house!