I won't be arguing about security. But i have remark about behavior of the portable version. When this version by default creates wallet somewhere deep in the guts of OS where is portability here? I believe that really portable version should handle data file in the same folder where executable is.
I know there is way to assign wallet file from a defined folder. But not create one. Also there are plenty people who able to backup folder with his/her data, but not that many of them able to write shell file to assign wallet file for this binary. Ask them to find where wallet was created and it will be a real challenge.
Portable version should be really portable, otherwise what is the difference with installation?
The portable version was 'fully' portable up to and including version 2.3.2 meaning that it created all the data folders, files and wallets within the folder from where the exe was started. You could thus copy the electrum portable exe file to a usb drive, start it up and it would create all the folders, files and wallets in the same location on the usb drive which made it 'portable'.
The later versions of Electrum-BTC however no longer functions like this. The latest binaries that were released do not even support Trezor anymore so not to sure what is going on with Electrum but I'm personally not very impressed with the way things are going. The 2.4 binaries have been out almost a month already and still no update to add back in support for hardware wallets.
Electrum_LTC portable on the other hand works as it should. Even the latest version, 2.4.3.1 works just fine, whether portable and or install versions. The portable version creates and or uses the folders, files and wallets within the same directory.
Not sure why Electrum-BTC no longer works that way as Electrum-LTC is essentially a clone of it so not sure why the LTC version can work properly, including with all supported hardware wallets, while the BTC version seems crippled.