Title says it all , please find some things that are negative vs other mod types .
I saw this thread when you posted it, and I've been giving it some thought. I own two REOs and they are very different from one another. You asked for negatives compared to other types of mods... This is by far the hardest question I've ever tried to answer on ECF.
OK. I own a 14500 mini (no longer made but they do occasionally pop up in the classifieds). Compared to any mod with a larger than 14500 battery, of course battery life is an issue. When I take the mini out for the day, I have to carry a couple of spare batteries. That is indeed a negative in my book because the reason I fell in love with bottom feeders was the fact I didn't have to carry a bunch of vaping supplies any more... But, if you get a new mini, it uses an 18490 so that limitation is not an issue.
Another negative... and this is a stretch... regarding all of the metal REOs is that you might develop a habit sliding the door up and down. It makes a "schlik schlik" sound that tends to annoy spouses, coworkers, and other innocent bystanders. - That sounds like a joke sort of, but that topic has come up many, many times in the REO subforum. And, I'm here to tell you that it can and probably will happen to you. I'm not normally a fidgety sort of person, but I've almost driven my wife over the edge with the "schlik schlik-ing" on more than a hundred occasions.
My other REO is a VV Woodville (also no longer made, but metal VV REOs do pop up in the classifieds now and then). There are two negatives compared to other mod types, and one of them is absolute nonsense, but enough people believe it that I suppose it has to be mentioned.
First the nonsense: Stacked batteries. It takes a pair of 18350s. The hysteria about stacking batteries in unregulated, unvented tube mods spilled over in to misconceptions about stacking batteries in regulated mods with proper safety features. A lot of folks believe a lot of untruths about stacking batteries, so it had to be mentioned. I personally will not call it a negative because I know better. ---
OK now that's out of the way, the only other negative I can come up with on VV REOs comparing them to other mod types is they don't do sub ohm and in fact the chipset can only produce something around ~12 watts max real world. I think the spec sheet for the chip from notcigs said 14 watts max, but none of the notcigs chips I've used can do do it real world.
Other negatives I could come up with all have to do with personal preference regarding form factor. Some folks just really like tubes so much they can't use a box mod of any sort. I'm not one of those folks, so it's hard for me to understand it.
That's it. That's all I've got. If you want to completely remove the hassle of carrying supplies and messing around with tanks or cartos or bottles of juice or whatever, and if you want a perfectly reliable device that works every single time you push the button - and is also beyond durable, get a REO.