I prefer FLAC. Even a lot of audiophiles dispute whether 24b and other higher formats bring anything more to the table. The public generally thinks that more information is better, but there may be some issues with the reasoning. Assuming both formats of the music come from the same master, there's little-to-no difference. Most of the extra data is outside of the limits of human hearing, thus doesn't create an audible difference.
Rather than spend money, space, and time on SACD's, etc., you might be better off investing in an external DAC (digital-to-analog converter) that provides better performance than a higher bitrate alone... or do both SACD and DAC, but the DAC first. You must have digital outs from your source and an external amplifier for for it to work though, so it's only if you're pretty serious about your sound.