Unique is a pretty decent powder in .38 Special at 5.0-5.5 gr with a 158 gr LSWC. I don't think it's very good for .357 Mag, mainly because it doesn't meter well.

I made the mistake of buying Speer #13 and won't make that mistake on #14.

Unique has been around for over 110 years. If there was pressure problems with 5.0 gr, it would have been noted decades ago, but it wasn't. Of course, Unique wasn't the powder of choice for the original .357 Mag and shouldn't be used to get close to the original.