There is no data in men with a dosage of 1 mg letrozole. However, there is with 2.5 mg daily:
G. G. T’sjoen, V. A. Giagulli, H. Delva, P. Crabbe, D. De Bacquer, and J.-M. Kaufman. Comparative assessment in young and elderly men of the gonadotropin response to aromatase inhibition. The Journal of Clinical Endocrinology & Metabolism, 90(10):5717–5722, 2005.
G. Raven, F. H. de Jong, J.-M. Kaufman, and W. de Ronde. In men, peripheral estradiol levels directly reflect the action of estrogens at the hypothalamo-pituitary level to inhibit gonadotropin secretion. The Journal of Clinical Endocrinology & Metabolism, 91(9):3324–3328, 2006.
It roughly decreases estradiol by half at that dosage. But it could very well be it would do the same at 1 mg daily.
Either way, anastrazole also decreases estradiol roughly in half at both 0.5 mg and 1.0 mg daily:
N. Mauras, K. O. O’Brien, K. O. Klein, and V. Hayes. Estrogen suppression in males: metabolic effects. The Journal of Clinical Endocrinology & Metabolism, 85(7):2370–2377, 2000.
I’d say they have similar efficacy in men. In case you’re interested, I’ve covered the efficacy of aromatase inhibitors in a blog post: https://peterbond.org/post/the-efficacy-of-aromatase-inhibitors-in-men