[R] How to decide between two theoretical distributions?

[Petar Milin]

Question that I have to ask has two parts: first, related to statistics,
in principle, and second, related to R-how-to, in particular.
In very brief, I have collected pretty solid sample for a phenomenon
that has two possible interpretation of how it is distributed in the
population; for example, beta and gamma distributed.
How it can be tested which model (theoretical distribution) suits better
actual data? Except some vague idea that bootstrapping or jackknifing
could be used, I have no further thoughts on that matter.
Could it be tested in R and how?

Sincerely,
Petar Milin