It all depends on the amp there have been great stereo amplifiers and crappy monos and vice versa.
In theory a mono block will be better but it is not necessarily so!
As per Audio Feil's comment quite frankly my Hurricane's outperformed a $11,000.00 very famous American made Stereo amplifier which by all accounts should have wiped the floor with the ASL! So again get off the band wagon that just because something is a mono or is more expensive or is a stereo amp or a mono it is better or worse.
Personally I have heard the JL 2 and the build quality is amazing I just was never blown away with the sound! You can also overspend and over build!
As with anything else listen and let the sound be your guide.