Talking of comparison between the Prochannel Quadcurve EQ and the new LP EQ, I couldn't resist highlighting my below observations, though they could be considered very minor or insignificant for many :
 
1. The PC QC EQ has a meter range upto -72 dB at the lower end whereas the LP EQ is at -60 dB minimum (or am I missing something ?)
2. The PC QC EQ has an amplitude display range of -18 to +18 dB. LP EQ is restricted to -12 to +12 dB (or am I missing something ? Can this be modified ?)
3. The PC QC EQ has a very useful frequency and gain indicator at the bottom right of the graph based on where the mouse is positioned when hovering over the graph. This useful feature seems to be missing in the LP EQ (or am I missing something ? Is there a setting for this ?)

The QuadCurve emulates analog EQ. Phase shifts in analog EQ are what gives its "sound," as these shifts cause amplitude changes above and beyond whatever you're boosting or cutting. The four curves (which to me are what make this EQ so invaluable) emulate the way different analog EQs work. For example, there are two curves that emulate SSL EQs, and another that emulates a Pultec-type response. These different phase shifts and amplitude changes account for the various "colors" of analog EQ.
 
Linear Phase EQ does not create these kinds of amplitude changes. This is why it often seems like adding a lot of boost with a linear phase EQ doesn't produce as obvious a difference as using "analog" EQ. LP is exceptionally good at EQing high frequencies. At lower frequencies, with some signal sources under some conditions there can be a phenomenon known as "pre-ringing," but this is generally not noticeable.
 
LP operation is also a big advantage with multiband compression or using a multiband as a crossover, because when the signals from the various bands are re-combined, their phase relationship is correct. However (to oversimplify) you need time delays to make sure these all line up, which accounts for the extra latency.
 
 

 
Thanks for those really useful notes Craig, though it will take a while for someone like me to appreciate the science of it.  Guess will have to do some more reading to comprehend the practical application of LP plugins.
 
But I did realize that using these new LP plugins on a final mix audio track does provide a strong platform to tweak the frequency spectrum to taste, in particular, as you explained, where over-emphasis of amplitude changes is undesirable, which is taken care of by the LP mode.
 
Where it gets more interesting is when you need a different treatment for the same band at different parts of the song including a case where you need to treat a band in the L-R mode in one part of the song and in the M-S mode in another part. That is when I guess automation of the parameters could help. I am yet to check though if the change of mode from L-R to M-S can be automated.
 
I just wish the bakers could do an update to both the LP plugins to introduce an indicator for frequency/gain at mouse point similar to what we have in the Prochannel Quadcurve EQ. This really helps to quickly identify the values and regions within the frequency spectrum analyzer.

ramscapri
 
2. The PC QC EQ has an amplitude display range of -18 to +18 dB. LP EQ is restricted to -12 to +12 dB (or am I missing something ? Can this be modified ?)

With the LP EQ in the upper left corner of the graph there are choices for amplitude range; 6 db, 12 db, or 30 db. Just click on the one you want to use.

mcstringer413

ramscapri
 
2. The PC QC EQ has an amplitude display range of -18 to +18 dB. LP EQ is restricted to -12 to +12 dB (or am I missing something ? Can this be modified ?)

With the LP EQ in the upper left corner of the graph there are choices for amplitude range; 6 db, 12 db, or 30 db. Just click on the one you want to use.

 
Oh yes ! Silly me missed that one. Thanks mcstringer413.