Direct answer: The 1/2 HP Eagle 2000 FR is rated for a gate up to 45 feet and 1,000 pounds. The 1 HP FR version keeps the 45-foot length rating but increases the published weight capacity to 2,000 pounds.
Power and backup also change
Eagle lists 115 VAC / 5.7 A for the 1/2 HP model and 115 VAC / 11.4 A for the 1 HP FR. Power I is the backup option for the 1/2 HP version; Power II is listed for the 1 HP version.