One of the Mini's main disadvantages is what exactly it will lock around. Scope out the area first to find out what you can lock the bike to. Take along a tape measure or eyeball it and determine which u-lock will work best.

You may also want to look into a beater bike if you plan on leaving the bike unattended for a long period of time. That nice shiny Redline I suspect would attract unwanted attention when left unattended. If you are looking into spending close to $100 for a lock perhaps that money would be better spent on something from craigslist or elsewhere.

Professional thieves I suspect would have the tools necessary to defeat any lock. However I doubt they would go through much trouble to take an X-mart or beater bike left unattended but properly locked. But that Redline might be to tempting to pass up. All locks are defeatable. How much time, how much effort, and is it worth the risk seem to be the limiting factors.