What's the best medicine for hair growth? And is nanoxidil better or minoxidil?

There is no such things a "best medicine" for hair growth. There is no generic medication for hair loss.  You need to see a doctor for a proper exam first.  Your doctor can explain various treatment options based on your exam.

Topical solutions in general are great tools to combat hair loss if used properly but unfortunately most patients do not comply with the directions.With rogaine, you are to apply in the morning and apply in the evening. The same holds true with nanoxidil however,  the proper dosage is 6 pumps 2 times per day. This becomes laborious for the patient to perform everyday and they wind up altering the treatment protocol thus reducing the effectiveness of the treatment.Capillus 272 has been the most effective modality for combating hair loss in our Cincinnati practice because it is so easy to comply with the instructions and it offers no side effects.

I use a combination of topicals and injections with prp and progesterone.  you need a long term plan for your loss, please see a specialist.  Best, Dr. Emer.

Minoxidil is FDA approved for hair loss. There are no other topical treatments FDA approved at the present time. 

The active ingredient that is FDA approved for hair regrowth is minoxidil.  Both have 5% minoxidil.  Nanoxidil has numerous other additives that have not gone through the rigors of an FDA application and I would be careful and stay away from nanoxidil,  because I do not have any information on stability, safety,  and efficacy of all those additives with minoxidil. 

Your question: Is nonoxidil better than minoxidil is answered with more knowledge than I have in the web reference below. Of course, you should consult with a good doctor about your hair loss problem before you become your own doctor.