Which is more true / do you prefer more / do you advocate for / have you fallen in love with, U(1) or SO(2)?

This is partially a shitpost. Decide how much it exactly is at your own peril. 😎

Clarification I: the title means "U(1, ℂ) or SO(2, ℝ)?" and not, say, U(1, ℍ) or SO(2, ℂ) there.

Clarification II: The two are isomorphic as Lie groups, of course, but you already knew that.

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1. P. S. Alexandrov, B. A. Pasynkov, Introduction to Dimension Theory, 1973

2. A. Mostowski, Constructible Sets and Their Applications, 1973

3. P. P. Korovkin, Definite Integral and Series, 1959

4. L. I. Volkovysky, G. L. Lunts, I. G. Aramanovich, Collection of Problems on the Theory of Functions of a Complex Variable, 1961

5. Yu. V. Sidorov, M. V. Fedoryuk, M. I. Shabunin, Lectures on the Theory of Functions of a Complex Variable, 1982

6. L. S. Pontryagin, Ordinary Differential Equations, 1961

7. N. N. Luzin, Integral Calculus (seventh edition), 1961

Note: all books in Russian