Two minutes with google scholar will reveal a few things…
a) In some individuals, testosterone does tend to be lower in users, BUT the levels still tend to fall within the normal range
b) In some individuals, cortisol levels go UP when using marijuana
c) “[marijuana]…cause an athlete to reach maximal heart rate at a lower than normal intensity of exercise, resulting in a decreased maximal work capacity” - Schatzberg AF, Nemeroff CB (eds): The American Psychiatric Press Textbook of Psychopharmacology, ed 1. Washington DC, American Psychiatric Press, 1995
d) “Chronic marijuana use has been associated with decreased motivation to perform and to give a maximal effort as well as with decreased circulating testosterone levels (8)” - Schatzberg AF, Nemeroff CB (eds): The American Psychiatric Press Textbook of Psychopharmacology, ed 1. Washington DC, American Psychiatric Press, 1995
e) Pulmonary problems are far more common in smokers of both individually marijuana & tobacco compared to nonsmokers to a statistically significant degree → Tashkin DP, Coulson AH, Clark VA, Simmons M, Bourque LB, Duann S, Spivey GH, Gong H
The American Review of Respiratory Disease [1987, 135(1):209-16]
f) TL;DR Smoking marijuana makes the ‘gas diffusing’ function of the lung less efficient → Marijuana smoking as cause of reduction in single-breath carbon monoxide diffusing capacity - The American Journal of Medicine
g) Vaporization is a safe delivery method of THC → http://www.nature.com/clpt/journal/v82/n5/abs/6100200a.html
h) Vaporizing is safer, again → http://www.biomedcentral.com/content/pdf/1477-7517-4-11.pdf
Etc.
Basically, it’s safer to vape.
I don’t smoke, through any form of delivery… because I have better shit to do