If this is referring to surveillance, police state etc., then I choose freedom. The reality with the increase of "security" is that more power is given to the government over the people and the already large hegemony between the two reaches even higher levels. Ultimately, that itself is a threat to freedom and security, as such power cannot be trusted. It is the ultimate contradiction, in my view, those who are putting this "security" into place are achieving that through fear and ultimately are just as much a threat to you as the evil archetype villain they claim to protect you from (terrorists, serial killers, communists etc.).
This isn't an either/or question if you present it like this without any qualifiers, it always depends on the circumstances. In the United States you can look at weapons for both sides of this issue: on the one hand people aren't allowed to keep nuclear bombs or cruise missiles or anthrax, demonstrating a prioritization of security over freedom, on the other hand they are allowed to keep pretty much all the small arms they'd like, a prioritization of freedom over security.
Few people would argue for freedom in the first case of nuclear bomb ownership. The second case is more controversial, but it suffices for this example that there are people who argue for freedom on this. So they come down on different sides of the question when the circumstances are changed.
As Montesquieu said : "a People that is willing to sacrifice its freedom to gain some security doesn't deserve either and eventually loses both." (on-the-fly translation by myself)
You can't possibly chose security : you always want more, the absolute security. But it doesn't exist and won't ever exist, so you just lost your freedom.
Then, the important thing is to define one's freedom.
My personal opinion is to prioritize freedom, but this is one of those questions that actually means very little in practice.
If you have absolute security but no freedom, you have nothing worth living for. And, since absolute security is impossible unless there is an omnipotent enforcer, one often is trading immense amounts of freedom for no additional security.
However, if you have no security, you are living a fearful life. Even if one is fearless, a life without any security isn't going to be free for very long, by virtue of not being secure for very long.
If you don't have a modicum of security, you can't make a variety of interesting choices. Commerce, marriage, friendships... those interactions are very difficult to form and maintain without security. The social contract at its base requires security: Hobbes was right about that.
In the vast majority of situations, I do not want to trade freedom for security because it means I am controlled by fear. Losing quality of life for freedom is in most situations a sucker deal. But the tradeoffs aren't linear: Sometimes, a little bit of extra security practically gives you more freedom than the freedoms lost; other times, a lot of freedom can be purchased by enduring a little less security. Worse, all too often, expanding security means giving the people who want to terrorize us exactly what they want. And short-term security benefits can trade off with long-term security benefits precisely because people resent freedom impositions.
In other words, this question is sort of like asking, "Should I invest in gold or securities?" You want to do both, and there's no simple formula to determinen the mix. You have to refer to other goods too. Freedom and security have to be considered alongside other goods like happiness, perceived freedom, perceived security, equality, etc.
You have to understand why we want freedom to get why this matters. Freedom isn't just an end to itself: It's designed to facilitate the personal growth and development of people, to give them the chance to learn how to be an ethical person, to give them freedom to make mistakes.
In that sense, security is a right to facilitate the same good as freedom.