If you want to get flats, I recommend finding a flat that fits your foot, your body and your racing.
Foot - Whether you're neutral, high arch or flat you need to flats, much like trainers, are designed for peoples strides.
Body - Additionally to foot shape. Shoes are made for body/ stride types. Some are for efficient mid-foot strikers and some are for larger heel striking type runners.
Racing - You can get flats that are meant for 5k and under to marathon flats. The biggest difference is typically weight/cushioning.
I have worn Nike flats for about the last 5 years. I have worn them for most of my track workouts as well as all my racing(up to 1/2 IM). I recommend bringing in your current running shoes to a running store and helping them find a flat should work well for you based on your current trainers.