First came the 7753 which looked like a 773F except the lift arms were black. Then came the 773F with the same lift arm design but with white lift arms, then came the 773g with the modern lift arm design. The earlier 773's have impaired side to side visibility due to the lift arm design. The F series has a BOSS computer management system compared to the G series with BICS. BOSS management isn't as desirable as the updated bics system. Also some of the F series may have a seat safety switch that has a track record of problems. Which will bring the machine to a stand still when it malfunctions. There is a over-ride kit available to bypass the switch. Otherwise both sport the same engine, and most likely the hydraulic system. The G has a nicer cab design with better heating/cooling capabilities if equipped with enclosed cab and air conditioning. Both machines are proven workhorses. The G's have been out long enough so finding decent G series shouldn't be too difficult.