My only experience with either is through my brother, who bought one of Promag's extended round magazines for a Taurus TCP-738. The magazine was absolutely useless out of the packaging, utterly incapable of loading a single round into the chamber without hanging up on the feedramp.
However, he was able to find a video on YouTube which illustrated a method of making the magazine reliable by modifying the feed lips with a pair of pliers which worked for him, but he never carried said magazine and used it strictly for range use because he didn't feel that it was reliable.

So if you absolutely must choose between the two, then go with Promag because at least they aren't known to fall apart and can generally be made to work reliably.

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Shooting Comfort is bilateral.