I have both a purge and a non-purge SeaVision. Neither leaks (well, all masks leak a tiny bit, occasionally, even perfectly fitting masks).
I have never had a problem with the purge, in any way. It's very small, tight to the bottom of the nose cup, doesn't interfere with the regulator, or equalizing.
In my case, I have a disk issue with my neck (too many sports injuries), so looking up to clear isn't as comfortable as it used to be. So, the purge is perfect. Never have to move my head to clear, which for me is more of a necessity, than a convenience. However, I don't see why, given the reliability of this purge, and the complete lack of issues, it can't be a convenience for anyone else that prefers to use it.