Obviously one is enclosed and the other is open. Some open platform printers with heated bed can print ABS, though we have only printed with an enclosed printer due to emission and odor. Temperature and emission are main reasons why ABS and other engineering materials are suggested to print with an enclosed printer. Some 3D printers even have HEPA filter built-in to filter UFP emitted during printing.
Another difference is the price. Enclosed printer is generally more expensive than an open printer with similar features.