Good to know about the 901s. I'll look into them.
I tried the Cannons', liked them okay but did not care for the whistle tips on them.
Any issues with either the 801 or 901 attys falling apart? I don't mean burning out, I mean coming to pieces like the first io6 I tried.
No nothing like that (I've lost a couple i06's to ultatight drip tips and one to the grateful vapor sleeve so I feel your pain!).
The 801 and 901 are much more orthodox in design. They come with whistle tips, but you can buy a couple regular drip tips to use with them. Any 510 tip will work on the 901 and can be found on Iken's site (among many other places) in the Parts and Accessories area, but the 801 requires a larger tip and I don't know if Iken sells them. They are easily found elsewhere.
I don't like to have to remove the tip for dripping, so I get wide-mouthed tips. And I chain-vape a lot, so I tend to avoid metal as it can heat up after a while. YMMV.
From what I understand the 510 cannons should be almost exactly the same as the 801s in every way but the threading. I haven't tried my cannon out yet to compare, but that is the impression I got from the site... I'm sure someone else here has tried both?