They have the same meaning except for that when you add "以", it sounds more like ancient Chinese. Therefore it sounds more formal, if I have to give a context in which I put a "以", it must be when I am giving advice to others. I mean I wouldn't say 我一定能给他以帮助，because it sounds a bit pompous that give a hint that I'm so much better than him that he should regard me as important as a mentor of his. But some people might say 你应该给他以帮助。or 这个故事给我们以力量 (see the different? When you don't use "I" as the subject, it doesn't sound as pretentious) ,though not very common.