If you're considering a GT-100 I suggest you also consider the Line6 HD500X. I've used both and sold the Boss unit. The boss unit has more flexibility, allowing you to tweak everything, but this also makes it more complicated to use. I am computer savvy. I love to tweak things. But this was so complicated I felt I had to learn it all over again each time I got it out. The Line6 unit is much more streamlined and straightforward. I spend time making music, not figuring out how it works. You can get great tones out of either unit. But usability was much more accessible with Line6 for me.
Please don't forget, both of the options you mention are really software simulators. The HW boxes run on their embedded DSP. The software ones run on the PC's CPU. There is very little "real" hardware involved in the HW boxes other than IO, knobs, switches, and a selectable input impedance. The "tone" is all due to software in both cases (granted, the selectable input impedance can have an effect as well).
I am big fan of the HW units for live performance. And, since I'm so familiar with it, I also use it for recording. But if I were to start now and only use something for recording, I'd go with the software option. The HW boxes are limited by HW. How much memory, how fast the CPU, etc. They are virtually impossible to upgrade. With the software simulators you have tons of RAM, tons of processing, and the upgrades are plentiful. They have a lot more potential for higher quality in my opinion.