Odin is clean install (wipe everything flash a fresh O/S). OTA is upgrade or dirty flash, you still able to keep your setup and all your installed apps. If your phone is running smooth without any issue then OTA should be fine. If you have weird issues, then Odin is recommended. I see you already have TWRP and probably already rooted that means you can not use OTA method and if you use Odin you will wipe out everything including TWRP, root, your setup all the download apps, system/user data and so on. Your phone will be like a new one. This bring us to the point that you will NOT able to restore 4.3 (you will need to reflash TWRP and so on..) and we have mix reports about once you on Kitkat it's not possible to flash back 4.3 due to different bootloader.