Howdy,
I own both and have been vaping for about 6 weeks give or take.
I started with the 650 twist, bought 2 of them, used mini vivis on top. They are great. Tweaked one of the vivis when I had the whole unit in my front pocket of my jeans, so now I had a dead vivi. Found an old flashlight holster, closed the bottom of it and carried it around my neck where ever I went. Remember, with the twist you need two of them, one to charge while you are using the other. I was a 1.5 PAD smoker. I vape more than I smoked. One batt would last me about as long as it took to charge the other. Then one of the twists just died.
After the death on one twist, I bought the LT. Love it, great device. Got 2 batts. One charges while I'm using the other. One device 2 batts. I made this choice because I knew, just knew, that I would end up with other 18650 batt devices, so I wouldn't end up having another type battery to deal with ( I also know that sometime in the future, I'll end up with a device that will not use the same batts). When I go out, I now carried two devices, a twist for when I'm wandering thru a craft fair and my LT I use while driving, cause if I don't the twist will die if I'm out more than a couple of hrs. I don't carry the LT only because I don't have a lanyard or pouch to carrying it around. If I find one then the twist will stay home as a backup and I'll just take the Tube and an extra batt.
Then I discovered the world of bottom feeders. Got my VModXL a few days ago, and it hasn't been out of my hand since. Uses the same 18650 batts ( see.... I knew it), and it fits in my hand my jeans pocket, my shirt pocket, etc., it's still too new too put down, lol.
My humble opinion would be to go for a Tube. Find a way to carry it that is comfortable to you. The size may bring a couple of stares, but myself, I don't care who stares. If the stares or the carrying a large and a bit heavy device around bothers you, grab yourself a couple of twists, get yourself a lanyard or pouch, wear it proud, or stick inside your shirt or jacket.
These are the only devices I own, and all three of them are great, all have their purposes in my vaping life. I kinda think, at this point, my VMod may end up moving the other two into the category of backup device, but at least I know I have 2 great backups!
Big Mac