The key is the condition of the planter. A well maintained 7200 is better than a worn out 1770. You really need to look at the vee opener discs, parallel link bushings, tail piece (a plus for the 1770), etc especially if the 7200 has had corrosive liquid fertilizer. Look it over very carefully and figure in whatever parts and labor it will need into your price evaluation. Good luck.

Jim at Dawn