I recorded a quick shootout between the Hairball, the CLA-76 and the UAD 1176LN using an electric bass track straight from a DI into an Avedis MA5 and converted with a Mytek Stereo96ADC. I was impressed that I could achieve basically the same sound with each. The Hairball was inserted during the mix via an Mbox3 Pro.
Input and output gains varied significantly between the units to get the same sound and meters didn't show the exact same gain reduction...but the post-fader signal meters in PT looked about the same in terms of total volume and gain reduction.
The .zip file linked below contains mono output files of each of the 3 units and photos of their settings. Each unit was set with a compression ratio of 4:1 with similar attack/release settings. The attack is at 12 o'clock and the release is a little past 3 o'clock on all the units.
Download link: http://grahamspice.com/docs/Hairball_CLA_UAD.zip
Sorry I don't have a vintage 1176 or reissue to add to this comparison. Send me one and I'll add it!