Real is way better, it is always preferable to eat raw, fresh food in its natural state where possible. I'm sure Jif would do in a pinch, but if you're planning to take hot water with a squeeze of lemon every morning then start buying a bag of lemons with your groceries I would.
I use the Hot Water and Lemon every morning and night! I used to but the fresh lemons but recently I have being using the jif, not really too sure if it does the same thing but it is great to keep in the fridge at work. I would imagine it would doi the same job as not only is it cheaper, it is also squeezed and made from 8 naural fresh lemons! x