Biotin 5,000 or 10,000: which is better?

It should not make a difference as biotin does not help most people with hair loss. I’ve attached an interesting reference below that you can review. If you decide to use, be aware of side effects (acne etc) and be sure to review with your health care providers how it can affect your blood test results in the future. This is  perhaps the most import thing to know about when taking biotin. I’ve includes references to these too.
References 
(1) Soleymani et al. The Infatuation With Biotin Supplementation: Is There Truth Behind Its Rising Popularity? A Comparative Analysis of Clinical Efficacy versus Social Popularity.J Drugs Dermatol. 2017(2) De Roeck et al. Misdiagnosis of Graves' hyperthyroidism due to therapeutic biotin intervention.. Acta Clin Belg. 2017.(3) Samarasinghe S, et al Biotin interference with routine clinical immunoassays: Understand the causes and mitigate the risks. Endocr Pract. 2017

Biotin is a water-soluble vitamin that's a part of the vitamin B family and whatever dose you take, it will probably make no difference. The use of Biotin for hair loss has not been shown to have value