Be careful with your search. The 2012 re-issue includes bonus tracks like "Part of Me" and "Wide Awake." While these are great, the mastering is slightly different—generally quieter with more headroom. If you want the pure 2010 aesthetic, ensure your FLAC rip corresponds to the original August 2010 pressing, not the 2012 reissue.
If you are listening on Apple EarPods in a noisy subway, FLAC is overkill. But if you have a DAC, a decent amplifier, and wired headphones (or high-end speakers), the difference between a 320kbps MP3 and a 2010 FLAC rip of Teenage Dream is the difference between looking at a Polaroid and the original negative. Katy Perry - Teenage Dream -2010- Flac
Musically, "Teenage Dream" is a masterclass in collaborative pop engineering. Perry worked with a "dream team" of producers including Max Martin, Dr. Luke, Stargate, and Benny Blanco. The result was a sound that blended bubblegum pop and disco-rock with electronic flourishes. While MP3 versions of these tracks are ubiquitous, listening in FLAC reveals the depth of the layers. The crispness of the synth pads in the title track, the explosive orchestral percussion in "Firework," and the gritty, futuristic basslines in "E.T." benefit significantly from the lossless compression, which preserves the original studio master's frequency range and dynamic detail. Be careful with your search
That quintet of chart-toppers included: