The Force is basically Ki, except more telekinesis based, or so it seems. They run off some of the same concepts: you harness the spiritual power of yourself and/or others to physically manipulate energy and matter. The Force (atleast in the movies) is explained as using a universal "life force" (Chi/Ki) that trained and gifted people can tap into and harness. Dragon Ball Ki is the same thing. You see Goku, Vegeta, Krillin, Beerus, etc train to increase the amount of Ki their bodies produce and store. Frieza/Freezer and Cell use telekinesis as well, a notable happening is when Cell creates his arena. It is also shown that Ki is similar to normal energy as we see Androids that can steal and produce and harness Ki. Ki is also like Star Wars' Force in which multiple people can pool their energy together to power up one person or create a massive attack. That attack is of course the Spirit Bomb.
TLDR; The Force is the same as Ki. This is from my rusty memory so if you have proof that they are VERY different then state your point.