I have been using the GT1000core for a few years. I just got an Anagram a few weeks ago and I do not regret getting it.
The the blocks in the signal chain are reserved for certain effects, for example, there are 4 delay blocks and you can only use them for delay.
There are dedicated distortion and chorus blocks, but the options there are not very good for bass. There are more and better options in the general FX blocks.
There are only 3 general FX blocks, but to make the GT1000core really shine, you need to use one of those effect blocks for a Mastering Effect, so that means you only have 2 effects blocks.
You mentioned the UI. Yes, there is a real learning curve to the GT1000core. I found that I also had to use a MIDI controller to be able too use the GT1000core live.
With the Anagram these are no longer a concern. Everything about it is superior and it DOES very well with clean sounds.
Don't get me wrong, the GT1000core is a very good unit and one I got used to how to use it, I really didn't have many complaints, but, as I said, the Anagram is far superior in most respects to the GT1000core for bass.