both are similar in prices... with the V Vocal not working well, I need a good, but inexpensive (< $150) vocal tuner.  I was going to upgrade from essential to assistant, but then I thought about the nectar upgrade, which apparently has some decent pitch adjustment built-in, very similar to Melodyne.  
For those of you that have both products, is the pitch control in Nectar 2 as good as the Melodyne assistant?  I do like the looks of the extra features from Nectar as well... I still use Nectar elements on occasion and thinking how convenient it would be to use 1 vocal bus plug instead of 5.
...my only other thought is that essential to assistant doesn't give me much.  There was a post in 2012 on Cake forums about this comparison but software has changed. 

How much is it from Essential to Editor? I think it was about $120.00 when I upgraded from X3 Essential. I would think that would be the way I would go but they both have merit.

For tuning, Melodyne is great.  I had just learned V-Vocal when Cakewalk bundled Melodyne.  I upgraded to Editor.  I also have Nectar 2 which I sometimes use for harmonies, and some folks rave about the plate reverb, but I've never used Nectar to tune vocals.
 
Some users have reported issues with the new version of Melodyne in Sonar.  There a few threads about that.

essential to editor is $399.  I guess I'm looking at the Nectar 2 suite which has the vocal blob editor like melodyne, not the basic nectar.

Nectar 2.
 
Just pulled the trigger on it. And no regrets.
I already had Nectar Elements, but got a good deal on Nectar 2.  No Regrets.
 

Nectar2 is pretty sweet. Swapped my Melodyne Essential for it.

Not sure what the upgrade price for Nectar2 Production Suite is, but this guys is selling it for $60 over at KVR: http://www.kvraudio.com/forum/viewtopic.php?f=43&t=456781&sid=55ef292f0ea5dbc392df0d4f65ce3c80

Maarkr
essential to editor is $399.  I guess I'm looking at the Nectar 2 suite which has the vocal blob editor like melodyne, not the basic nectar.

Yeah, at the time the upgrades were on sale, but isn't Essential capable of tuning?

you can pitch change essential, but assistant has additional tools for pitch, vibrato, formants, amplitude, etc...
 compare here:
http://www.celemony.com/en/melodyne/editions-and-technical-matters