>>> I'm adsense publisher but my earnings dropped 75% last month without any reason for.
You're not alone [webmasterworld.com].
>>>1) You can't use both together right? I mean you have to remove all adsense code from pages and put YPN instead.
You can't use them both on the same page. However, last I checked, it was ok to use them both on the same website. One reason a site might have to use them together would be to geo-target which ads show. Doing so (showing U.S. users YPN and non U.S. users adsense) can help keep you from getting that dreaded email from YPN terminating you from the program for too much non U.S. traffic and can help you actually earn money from non-us visitors by serving them ads actually targeting to them by Google.
>>>If so how are you doing in comparison?
For me, it has depended very heavily on the industry.
>>>Being in latinamerica doesn't help in that way
YPN is currently limited to publishers based in the U.S.
>>>the manual ad targeting feature didn't allow us to select the exact niche that we are in so we selected a somewhat similar niche, which did paid well but I guess didn't convert well for the advertisers
IMHO, then it was totally fair for them to disable it. There is a huge abuse in the categorizing options. I'm not saying that *you* abused it, just saying a lot of people do, which causes scrutiny in regards to it.
>>>YPN beats the pants of Adsense, you just need to test and try
The only problem I've had, and I don't know if anyone else has noticed it, is that if I remove a quality site from Adsense and put it on YPN and then switch back, the ecpm goes to crud while Adsense "re-figures" its conversion and value to advertisers to give us better ecpm's based on smart pricing. I've found it is better to A/B test (or YPN on some pages, Adsense on others if you don't have the sophistication/budget/expertise to A/B test) rather then remove Adsense all together. Maybe it's just me, but that has solved some issues for us in regards to occasionally pitting them against one another.