why are people never happy with what they have? I don't intend to be mean in writing that. Rather a find it pretty fickle to be always on the hunt for the "best" everytime new "shiny" comes into view. We all tend to fall into the trap no matter how much we try not to...but in this case you have a device that works just fine.
Are there Kindle books you want that you cannot get in epub? That would be the only justification I could see...now if you can sell your Kobo for essentially what you paid, then sure why not? Of course ya do lose the legal ability to checkout library books.
You could look at it this way, with two readers, your Kobo and the hubby's Kindle you have all the bases covered. Of course trading devices might onvolve prying the Kindle out of the hubby's cold dead fingers before the cops arrive. hehehehe...
Really, do what makes you happiest as long as you can afford it. You are not a bad person for being distracted by unproven "shiny"...because, well, it's "shiny"...