To add to all the replies above: I've had both and currently have the Core and a Helix LT.
The Core is MUCH more powerful than the Stomp, I found it very easy to run out of DSP on the Stomp and it's probably even easier now with the recently added higher end effects. The Core is more like the Helix Floor/LT in DSP power.
I find that overall the Core sounds better and less artificial than the Helix, although this is purely objective.
There's a lot to like about the Helix family that I wish Boss would adopt, in particular I find the Line6 desktop editor to be much more user friendly than Boss's offering such as the simple fact that Line6 offers multiple levels of Undo! The Helix editor also has a lot more free slots to play around with.
The reason I keep the Helix LT around is that Line6 is MUCH more active in releasing new effects and updates than Boss (This is not even close!) and Line6 people are active in these forums and directly respond to their users. Another reason is that the real-world modeled effects in the Helix have a certain fun factor that is missing from the Boss offering.
It's not all roses in Helix land though, you have the very real running out of DSP issue and Line6's rather poorly planned default settings for many effects means that browsing different Amp or Drive models can be like walking on a minefield - You never know when changing a block will blast you with levels that are as much as 15dB higher than the previous preset. On top of that sometimes having dozens and dozens of Amps means that end up not giving a crap about 95% of them. More is sometimes just more.
That all being said, I use the Core much more than the Helix, for the all important reason that I like the end result much better with the Core.
(okay, you need an adapter cord for the sends, not cool)
. The CORE UI is not very good I think, but that has nothing to do with the screen IMO.
