Dan and others,
When comparing the options, first think about what you want from the radio/modification process.
If you are a tinkerer/programmer and want to dabble in the software, the TSW solution can make sense as it is open source and you have a lot of memory and speed available to add things.
If you are more into operating, then I believe that there are more options available with the KD8CEC/Nextion including IF shift, Attenuation, Spectrum Scope, and others when a 2nd Nano is added. You should look through all of the choices on the HamsKey.com blog. One of the big ones for me is the Memory Manager software that does not have an equivalent on the other choices. There is also support for an SDR link to have a panadapter on a linked computer with many SDR dongles.
The last thing most will consider is future upgrades. I would not put too much into this category, as the v6 changed a lot of the future direction recently, and that can happen again. With that understanding, we have not heard much from Dr. Ian Lee recently. All of his code is open source, so anyone could pick it up and add a new feature. The TSW activity is recent, focused on the new v6, and also open source. All of that makes it a wash for me.
Hardware modes like AGC, Speach compression, CW audio filters can be done on any of the above mods.
If I were just starting with the uBiTx, the order would be:
1 - First get it working as supplied by HF Signals.
2 - Fix any hardware issues like the mic problems. Clean up the sound (small mod to the LM386 to remove hiss). Install diode protection if it will be near higher power transmitters without a grounded antenna input.
3 - Try out the FREE software from Reed to improve operability. You can always go back, it is software.
4 - Add an AGC mod. I have not done this yet, and have two different versions to try. I would suggest one that reduces gain prior to the audio sections, either at the first RF sections or the IF sections.
5 - Then go for more complex upgrades based on what you want to do with the radio. I have 3 and have focused one on digital, working on one for CW and a general use radio with ease of use items.
6 - Add a linear amp.
Above are my opinions. Others may be different, and that is as it should be. You need to make your own choices and live with the results.