Which is more difficult to learn, Hindi or Tamil?

If you are proficient in a language that's gender neutral,like English,mastering Tamil would be easier. But if you can speak a language that isn't gender neutral (which I consider more difficult) Hindi shouldn't be a problem.

I expect Hindi to be objectively easier, because it still belongs to the Ind0-European language family. I had no trouble learning it, in any case, while I have felt too daunted to even try learning Tamil. My late professor in Belgium was fluent in both, but my university did not offer a course in Tamil at the time. For some reason the question of which one was easier never came up. Subjectively, however, I have a theory that any language becomes "easy" as soon as one becomes motivated to learn it.

Tamil will be easier. Particularly because both English and Tamil have the same representations for 'Neutral Gender', which is used often in conversations (I mean there is no 'It' & 'That' in Hindi, we have to go always with 'He' or 'She' for neutral stuffs like car, van, pen, cat, etc). Understanding and instinctively using Male or Female genders for Neutral things will take more time. And the basic grammar of Tamil is somewhat similar to English than Hindi. Moreover, http://en.wikipedia.org/wiki/Tamil_literature is so vast that you can go deeper & deeper when you get a handle of it. One thing to note is Written Tamil is different from Spoken Tamil but in Hindi's case it's not that different. So, spoken-Hindi will become somewhat easier if you read many Hindi texts.