Is it a plus point for my PhD application to mention that I am already a PhD candidate at some other university? I have recently completed my MS and joined as a Ph.D. candidate in the same university. But I want to move out. I am filling the application for an other position where they have asked the following:

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There are options to mention that I am currently a Ph.D. candidate. Is it a good idea to mention that I am currently a Ph.D. candidate? I am asking this because someone have told me that if you are currently a Ph.D. candidate, universities don't give much attention to your application.
I can't really see how it is a plus, but it could be a big negative. 

The obvious question is going to be: why is this student leaving his current university? Doing a PhD involves a pretty hefty investment for both sides, and you're about to leave a university in an attempt to go to another. Universities want to be convinced that you will make it to graduation.

I would expect you to have a very good reason for this (trying to go to a better ranked school after starting at one isn't a good enough rationale to me).