bazbroom,
I don’t know what your needs are so take what I say with grain of salt.
I know of 6 different versions DS201 in 3 physical forms on the market. Pictures here seeedstudio.com/wiki/DSO_Nano
These I know, maybe there are others…
Version 1. DS201/DSO Nano v1
Version 2. DS201/DSO Nano v2 old LCD
Version 3. DS201/DSO Nano v2 new LCD
Version 4. DS201/DSO Nano v3-external mSD slot
Version 5. DS201/DSO Nano v3-2MBytes built in memory
Version 6. DS201 PRO/DSO Nano v3-8MBytes built in memory
Depending what version you get will dictate if you can have a fully functional Benf 3.64 or not. Since Benf firmware was written for external MicroSD in mind and the old LCD, it will work on versions 1 and 2 just fine. Then you can load Benf 3.64 patched v3 on version 3 and 4, again fully functional. It will also run ok on 5 to 6 versions minus the Saving/Loading functionality. Some people did get Benf working fully on version 5 to 6, but it requires soldering in the external MicroSD slot/card.
I personally own the DSO Nano v2 old LCD with Electron 007 firmware and it works for me but I am droolling over DS203. Therefore I will recommend getting DS203/DSO QUAD hw v2.81+ and load Wildcat 6 on it.
Good luck.
P.S. If you do get the current version 5 then most likely it will have factory 4.30 firmware. It seems to work ok and does Loads/Saves files to built-in memory. I would NOT recommend the version 6 because the lack of firmware development.