I tried clips many years ago, promising to persist for at least three months. In the end I did 18 months on clips. But it was my first sortie into proper mtb territory that persuaded me of the benefits of flats. You see, I just could not unclip when my knee was at the top (or near) of the stroke. Cue many comedy falls - only funny to onlookers of course. I picked up a lot of cuts, scrapes and bruises and serious near misses. So, I switched back to flats and apart from a short adjustment period trying to unclip a 510 Freerider from a flat pedal (enduring yet more comedy falls!) I got on absolutely great. I use the clips now and again just to keep my eye in as it were but only on local roads, nothing gnarly at all. I have learned my lesson.
I have no idea whether an emtb changes the risk/reward equation, but I suspect not (I haven't tried it). You are either comfortable with clips or not and on anything other than easy terrain, I'm not. It is worth a try just to add a new skill to your repertoire, but do yourself a favour and go somewhere easy to start with.