I'm looking at different EQ's and attempting to see if there are major differences between them. Since I've never had a better EQ than the  ones in T-racks, Scheps 73 which is really a channel strip but it has an EQ and the Pultec copies Waves makes. I still make use of the EQ in Sonar quite a bit mainly because it's handy in the PC and it is a decent EQ. I have many of the other ones but they are all similar....in looking at what is out there Fabfilter Pro-Q comes up a lot...and now they have the Fabfilter Pro-Q2. 
 
I'm not really super hip to the innards of these things although I'm learning as I go. Sometimes we don't know what we're missing until we know what we're missing....and I get the distinct feeling the grass really could be greener in this case. Frequency separation in a mix seems to make all the difference and the less well designed EQ's seem to exhibit interference between filters...apparently there are good ones and better ones...or at least a better way to design filters in software EQ's. Maybe I'd be better off just downloading a few demos and giving them a shot. 
 
Are there really: Big differences between EQ's ? If so, What makes one EQ better than another EQ ? 

Starise
 
Are there really: Big differences between EQ's ? If so, What makes one EQ better than another EQ ? 

GUI?
 
I keed I keed
 
It's the presets

Seriously though, i imagine to the purists (of which I cannot claim that title) it may be about
 
1. Faithful to the emulation
2. extended features (ala Melda's MAutoDynamicEQ)
3. transparebcy
 

From a DSP perspective unless they add analog modeled saturation/distortion, an EQ should change the frequency and phase response and nothing else. It is possible for there to be noise/distortion due to calculating precision, but I don't think this is a real issue today unless very deliberate tradeoffs were made. And there also can be sonic issues when adjusting the parameters, but once the EQ curve is set and static it just does its thing.
 
So all the rhetoric about any given EQ is either because it has nice EQ curves (the curves that any given EQ can create can vary a lot) and/or a nice interface with intuitive operation so that one gets nice results quickly and easily, and/or other saturation effects are added to it, or is based on the idea that if you give someone more money they can add 2 + 2 better than someone else.
 
IOW for the EQ part of any digital EQ, objective quality is pretty much a given in today's world. But that doesn't mean a given EQ can't produce subjectively pleasing results much more easily.

Because I'm not as adept as most (using one EQ for all purposes) I find that some EQ's are more responsive to specific instruments. At least that's my take on it.
 
Some examples are:
UAD Helios for bass
UAD Harrison for snare
Pulteq for guitars
 

Either that or an older boy made me do it.
(buy a considerable number of EQs)

without emulations of classic hardware, its all about ease of use (including preset curves).  For whatever reason, I love the EQ in Izotope Alloy.  Easy as hell to use, big GUI, sounds like a digital EQ should: invisible.

The best EQ for you will depend on your personal preference with regard to GUI and how well it gets you the sound you're going for.  So extensive demoing is a must.  For me, an intuitive GUI, low CPU hit, and stability are big factors.  I love Pro-Q2, but some don't get along with it for whatever reason. 
 
Here are a few general-purpose EQ plugins worth demoing, in addition to those already mentioned:
 
Acon Digital Equalize
Eiosis AirEQ (requires iLok)
AOM Tranquilizr
OverToneDSP AF2-10 (super cheap!)
 
Cheers,
Eddie
 

Slate VMR Brit-N

or DMG Equilibrium

or SIR Standard EQ

or Slate VMR 4k

mike_mccue
Slate VMR Brit-N

or DMG Equilibrium

or SIR Standard EQ

or Slate VMR 4k

Do they all go to 11?