I think it depends upon what you mean by "best". They each have their pro's and con's. For example some are better for bulking and some for cutting, some have harsher sides and require more involved PCT, etc.
I've used Helladrol, gained 25 lbs and kept 10. Kept the strength gains as well.
Beastdrol (superdrol) is also highly recommended and is supposed to be a stronger compound. I didn't want to try something that strong for my first cycle, so I haven't had any experience with it.
Bear in mind those are both methylated so no more then 4-6 weeks (4 for the superdrol) and you will want milk thistle / liver support supplements.
There is also something called Katanadrol that is supposed to be a good PH for cutting. Also, its not methylated. That means its not hard on your liver, but you have to take a lot more because absorption is much lower.
All the ones I've mentioned so far are available at Mr. Supps. People rave and rave about Superdrol (beastdrol) and I've seen some amazing logs of superdrol cycles on the net. I would give it a shot next but I'm gearing up for my first test cycle hopefully here soon. There are others, m1D is supposed to be very powerful. I've also been reading a lot about people saying that they are having real good luck with some topical DHEA products, I don't know.
I'm no seasoned vet to this, but that's about what I know at this point. I'm sure someone else will come along and give you better information. The only one I've personally cycled is helladrol and I had good results. Make sure you get some joint support (msm, chronoditin (sp?), glucosomine) from walmart or something though if you go that route. That **** dried out my joints something fierce. Then again that is probably something you want to do no matter what you cycle.