Summa if on top of my list since I'm already used to how they work. So I assume the learning curve will be simpler. Could you elaborate on why the summa is better since you have both of them?
I can approach this in many ways but in a nutshell, I think the Graphtec sucks. It feels cheaper, it doesn't track as well, it skews cut vinyl over a short distance on a regular basis, weird errors, have to reset it a lot to get it to work, reading barcodes is spotty at best, the menu is a disaster, it's slower, vacuum seems weak compared to Summa, the roll holder design looks like an afterthought, it doesn't slowly advance the material before cutting so it yanks the roll off of the roll holder unless you pull the right amount off before cutting, the USB (I know Burton) option doesn't always pick up all of the files that are on the thumb drive.... I'm sure there is more. I had a chinese cutter and honestly feel like it was more on par with the Graphtec than the Summa.
The Summa is fast, it is pretty consistent in cut accuracy, media never buckles (so far), it slowly unwinds what it is cutting so it's not jerking on the roll, the whole machine feels more robust, the menu is intuitive not some chinglish crap. I don't like gosign but there are other options and the setup videos from Summa suck, Graphtec has better online guides for setup and use. I like cutmaster better than gosign but both leave a lot to be desired so it's not really a factor IMO.
We don't do really use perf cut on either machine, it's too slow so can't offer an opinion on that. I think the Graphtec requires you to move the blade holder to perf which is stupid if thats the case, Summa will do it all in 1 go. The channel is a nice idea but the machine is lacking in too many other areas for it to be worthwhile.
Maybe it's just me? Operator error perhaps? Either way, that's my experience with the 2.