I prefer IR's, but flash cams have a place. You get more pics out of an ir per set of batteries. I know that doesn't sound like much, but a cheap flash cam will eat more than its initial cost in batteries in a year if you are not careful. In most ir's a set will last all year. One trick to extend battery life on a flash camera is to set the delay at 10 minutes. All of my ir's are set at multiple shots per minute. Simply put, it is numbers vs quality.
And far as reliability, they all stink. A well built camera is expensive, more than a couple hundred bucks. The customer service is a huge deal with trail cams.