901 has very good flavor and vapor but I found them hard to clean and they will drip liquid out a hole in their side - while they worked well they were nice and then they weren't. The barrel of my two also rotated relative to the threads and that caused some kind of plastic armature in the coil compartment to block the air intake in the side, ruining the drag. I would never buy a 901 because it's hard to find manual
batteries, many of its nicer PCCs don't accept manual batteries, and you can put a DSE901 atty on a KR808D-1 battery which is more popular (the most popular 2-piece and a real 3.7v slim mini). 901 lovers exist but I am not one. If they kept working well, I would love them despite the leaking. but that is just the attys. I would not love the batteries - hard to find real DSE901 cartomizers and though KR808D-1 cartos fit, some need an adapter to get airflow. IMO DSE901 is an atomizer to try on a different model (KR808D-1 or there are adapters for others)
510 - never used them. I have them. 3/4 of my ecigs are 510-threaded. I use cartomizers. I have heard 510 atomizers give a nice strong hit but not as good flavor as 901. 510 is the most popular threading.
306 - not a popular model as an ecig but the threading matches 510 and people with fat battery models and mods (they can use low resistance attys and cartos) many like the LR Cisco 306 atomizers for dripping. I do use a standard resistance 306 atty for dripping on a manual slim 510 to test juices. Steel, small, drip tip sort-of fits over it, easy to blow out and clean.
801 - many like these a lot for dripping. I plan to try an 801 atty. These are fatter attys belonging to a true pen model - the mouth end is fatter like a fountain pen cap and that is the atomizer..
As you see, I cannot really compare them since I have only tried 901 and 306. My batteries and mods are the two threadings that have good support for manual batteries and have the most stuff: 510 and KR808D-1 (can use 901) and to use other attys I would use an adapter. But I do 95% of my
vaping with cartomizers. Cartomizers are the most popular way to vape. A bit of a recurring cost but less hassle and more consistent. I use atomizers to test new juices and occasionally vape juices that I don't put in cartomizers.