I think the only difference between the disposable 510 and the normal 510 is the battery life. The box says "The Battery is At least 3 times rechargeable."
I can't comment on the truth of that statement since I only bought it for the atty and carts, but I've heard varying things on this forum and others. Some say that it will die after a few charges, and others say that they've recharged it 30+ times with no issues, so ymmv.
Also, the answer to your question about whether or not the 510 is worth it is subjective. If you're talking about the disposable model specifically then I'd say probably not because it only comes with an automatic battery, whereas the 510 really shines with a manual battery.
If you're talking about just atomizer performance, then I'd say definitely yes, it's loads better imo.