I have a SCSI2SD as well but I have it in an external enclosure so I can swap it between my Macs. I keep thinking I should put it inside the SE, but it's a pain to get out if I ever need to update the firmware or take the card out. Plus the enclosure raises the height of the screen to a better level for me (I'm kind of tall).
Yeah that's what I figured. So other than the look there really isn't any advantage. I might just get that keyboard and keep it as a backup Mac just in case. Then again after all the repairs I had to do on the Plus there's no guarantee that it won't die on me.
I actually traded my Plus for an SE that I repaired about a year ago (I still have both, just use the SE on the desk now). I have found zero compatibility issues with old games. Everything runs/plays exactly the same. The SE is a bit more convenient for every day use with the internal SCSI2SD, and I am using an FDHD model so it makes a bit easier in that sense as well. The positive I love about the Plus is the keyboard and mouse, which are built like tanks compared to the ADB stuff. Sounds like those are missing, however, so it wouldn’t matter.
For day to day use, I’d use the SE over Plus. Keep it if you like or trade with someone, I’d say.
A Plus and an SE with the same amount of RAM* should be almost 100% compatible. The SE will be a bit faster due to architecture improvements, and of course has the fan (though I think heat-related failure rates of pre-SE Macs are generally overstated) and internal SCSI if you like that. I don’t have an SE at the moment but would be surprised if it broke any games that work on a Plus (of course, the really old games might not work on a Plus in the first place).
* noted because old games that inappropriately assume the screen buffer is in a fixed location can be broken just by adding RAM