If you are a "spend the day at the parks" type and think of a motel as "all you do is sleep there" type, then definitely "save" money by staying offsite. The Hojo and Candy Cane Inn have many fans.
If you want your Disney vacation to include Disney amenities then you stay onsite. Those amenities include automatic MM admission, the ability to charge things to your room, excellent pools, restaurants, bars, and being surrounded by the magic 24/7, amongst others things.
Its a personal choice but on this board, most people will encourage you to stay offsite. I'm the creaking door that favors onsite. Its not the same level of immersion you feel at WDW, but it can be pretty close.