I am going mountain biking this upcoming weekend. It will be my first single track excursion since last fall with only 3-4 times last year. I always rode platforms and 510s until last spring, a year ago, when I bought some m520s for my gravel bike and shortly after I bought some Trail XT clipless pedals for my mountain bike. Honestly I have grown to love clipless bar none. But I got a decent set of Wellgos laying around and I still have my 510s and I am considering switching back for this upcoming weekend. As much as I loved flats, it seems as if my feet never "stuck" to them with my 510s like you read about online. Everytime I would go over rooted,rocky, or bumpy stuff, my feet seemed like they would move and shift requiring me to reposition them and on one occasion I remember, my foot slipped off. I am open for debate. What do you guys prefer?

I feel like you answered your own question with the 'bar none' comment...

BUT, if you want my opinion: I went clipless and never went back. Don't intend to.

I also have some long hiatuses (months, a year, etc.) and go clipless every time when I ride for the first time in a while. Do I fall over sometimes getting back into it? Maybe, but it's rare and worth the risk.

I went back to clipless because I start clipless and never got the hang of 'dabbing'. I just crashed with both feet on the pedals. That and had a hard time finding good shoes for flat pedals.

Good (flat) pedals make all the difference in the world, in my experience. My 5.10s grip like velcro on Spank Oozy pedals.

I had some Saints at one time and I feel like they grip just as good as these wellgos. It is kind of nice to jump on your bike and run an errand around town and actually be on some solid petals in your regular Street shoes. My clipless pedals aren't going anywhere. I've just been getting the urge to get back on some platforms for a while and I can't make up my mind

I keep saying I'm going to go back to platforms. I've developed a lot of bad habits thanks to clipless pedals.

I tried riding clipped in on my Mtb, but I just couldn't make the transition complete and comfortable because I dab a lot when riding.
2 weeks ago, I did a simple slide out and hurt my left knee because it did not unclip, so I am done trying that. I've never felt handicapped getting over/past obstacles using flats. I ride my road bike clipped in with no issues at all.
Almost all of my riding buddies ride clipped in, and they often fall because of it, yet..... they keep on riding clipped in. I tried it, and it was not for me. Neither is wrong, neither is right for everyone so we must decide on our own.

I can relate to what you just said. The first day I put clipless on my mountain bike a year ago, and I went riding some really technical stuff down in Kansas, I had all kinds of issues. I fell over a few times. Luckily I didn't get hurt. That was mainly due to being new to clipless and since then I haven't had any issues. But I've only been on one real mountain bike ride since then. The rest of the rides on this bike have been gravel rides and things like that. I love being clipped in because it makes me feel like I'm part of the bike. But I love being able to get off real fast if I'm trying something hairy or technical and being clipped in sometimes doesn't allow me to do that. Even if I'm falling over and I get unclipped a lot of times by the time I do get unclipped it's still too late. Too bad you couldn't have the benefits of both in one pedal LOL.

Something funny that happened to one of my friends, on the one and only mountain bike ride that I was on clipped in last fall, was when my friend Bill tried jumping something and the bike took off from underneath him and his feet stayed clipped in and he went flying down the hill on his ass with the bike in front of him LOL. Luckily he wasn't hurt and we all had a good laugh but he bent his Brooks saddle. Luckily we were also able to fix his saddle LOL.

What is 'dabbing'? I've never heard of it.

I of course mean whatever version is relevant and previously mentioned in this post.

Not Cam Newton dabbing...

Dabbing is when you place a foot on the ground for a brief moment to help with balance, usually immediately after a technical part of a section like a rock wall, slow speed tight turn, etc.
I raced MX/SX most of my life, so have a foot of the pedal (foot peg) and on the ground seems natural to me. I just can't unclip fast enough to save a fall

I've done that a few times and I've seen other people doing that. I didn't know it had a name though LOL. Thanks for bringing that to my attention I will remember that in the future.

Dabbing is putting your foot down.
Also, riding flats this year and its great. Much more control and connection to the bike.
Try this - https://learn.ryanleech.com/p/the-flat-pedal-challenge

One plus I've found with flats is that I can easily change my foot position for different pedaling techniques. Most of the time I pedal with the ball of my foot more or less centered over the spindle, but I also like to move my arch over the spindle in order to use different muscle groups (arch-over-spindle position works really well when climbing out of the saddle).