So tell me something Mr. lightgeoduck, if you have tried a M401, how might the KR808D-1 compare? The question assuming, which unfortunately I do often, you've tried the M401!
I'll try that one, Joker
it's no secret I think the M401 is the beemer of mini's. It's a real smoke machine that you can keep vaping as long as the atomizer is wet and the atomizer doesn't overheat. You can cool the atomizer quickly pretty much just by taking off the mouthpiece/cart. Like any mini, you can use the carts as mini cartzers, just putting on a new one when the old one is vaped dry. The mouthpieces do brittle up after a while and need to be replaced, although the inserts stay pretty unscathed. The battery life is pretty awesome.
The V9-compatible KR808D-1 can put out some decent vapor but nowhere near as much as long as the M401. The compensation is, flavor is amazing compared to the M401. and even zero nic hits the back of your throat in a much more pronounced way than the M401. Battery life is much shorter on a standard 901 battery than a M401, unless you have one of those 380mah batts (who is it that carries those? vapor4life?), so you'll need several thru the day. The V9 battery lasts a little longer, but still not as long as the M401 imo. Refilling is definitely less of a hassle than refilling M401 cart inserts since you're not doing it every day or dealing with tiny cart inserts. But there's no way to squeeze out the liquid that lingers, as you can the M401, so eventually the KR cart is going to need to becompletely rinsed out and dried (or just tossed). The cart-zers can be dripped on, although to me it seems too much of a hassle when you can just unscrew the cart and pop on a fresh one.
The E9-compatible KR808d-1 cartzers are also Kanger inside, but have different threading and require a different battery. so be careful whether you're ordering a E9-compatible or a V9-compatible cartzer. They are also similar in vapor production to the V9-compatible, since they are the same innards (except for Greencig, which is different innards from them all). I'm hoping the mods will come up with an adapter for the E9>V9 and V9>E9, seems simple enough.
In my experience, with inner cart burning in mind, the KR808D-1's are better suited for relaxed smoking - for at the office or when you don't want little bottles of e-liquid around - take a few drags, put it down for a while, take a few drags more. Repeat. Switch carts to a cool one. Repeat. The KR808D has to have time to wick and takes longer to cool down since it's totally enclosed, so cannot be the steam locomotive the 401 surely is.
Of course, the V9 USB case is nice - it's the same size as the regular 901 case, btw, a tiny bit smaller than the M401 hardcase, and takes several hours to re-charge a battery. You can fit the 901 batts in the case, although there is a caution to not charge them more than 5 hours before disconnecting and turning them around for storage. (the V9 batt has a intelligent chip that cuts them off after they are fully charged so they don't overcharge). E9 batteries will not thread and so can't be used in the USB case. You can usually match or sometimes beat Eastmall prices on carts and USB charging cases buying from vendors stateside, using their coupons.
I like M401's and KR's equally well for different reasons and so will most likely bounce back and forth between them.
Hope this helps!