If you are lifting in the USAPL, you can't use briefs at all...The IPF approved list is here:
For the USAPL:
I got next to nothing out of a Champion, but have seen a gent get about 40 pounds out of a crazy-tight one...I wasn't particularly impressed by either the Champions or the Z-suits, even considering the low price.
I've never had a Hardcore, so I can't say much about them but that they are fairly expensive ($135).
Elite has the Older Metal IPF-Squatters on sale right now for $90, so price-wise they are on par with the Titan ($85), and I would recommend one of those. The Metal has more spring, the Titan has more stop. Based on that I prefer the Titan but you may like it the other way around.