I used both and both are fine. Magisk does more things, and can somehow replace xposed for newer android versions that don't support it. Regarding OTA, you still can update, but the thing with both is that you need to reinstall them with each update, so it makes more sense to download the zip so it's just another zip to flash after the other in recovery. I once tried to update with OTA but seriously it doesn't make sense at that point.