To be honest, I am not a big fan of 801 attys nor carts. It's one of the reason I'm staying off from certain mod(s). Probably it's user error, but if I can't use it for whatever reason, it's not for me. Smaller mini atomizers seemed to work better for me and still does. Maybe it's the way I draw or what not. 801 attys were just way too easy to draw - and since I used to pack my cigs pretty tight to have hard draw.... so I like my 4075 and 901 attys much better than 801 - even with inconvenience of having to top-off or drip more often.
Anyhow, I have both 4075 and 901 attys for my SD. I use 4075 for the carts - great vapor production and throat hit. I use 901 for dripping - because the wick is more accessable. I get much more kick out of 4075 attys - but I have mouthfull of yummy, non-burnt taste and tons of vapor with 901 atty.
I had some fruity juice cocktails, which I didn't like with my previous ones... just tasted so meh. Now with 901 dripping method, it's the most frequently visited juice in my collection. I thought I'd never be able to use it up - and almost about to throw-away the whole 30ml - now I'm in love with it.
However, if I do want some kick, I go for 4075 with cart, filled with 18-24mg - and total satisfaction.
Remember, SD is one of the first commercially available mod - and things do get improved over time - and I'm sure the newer mods probably would surpass SD's performance for good margin. Most of them are also cheaper than SD as well and I'd like to have them too... But SD is giving me total satisfaction at the moment, and I am planning to use this for at least a full year before I consider getting any other mods. (and so help me god.
) Catching up with the Joneses would only cost me more money, and I already spent so much money of various e-cigs. It's not like I need 2 e-cigs in my mouth simultaneously... oh wait, I know people who vape 2 901s at once. 
Anyhow, I have both 4075 and 901 attys for my SD. I use 4075 for the carts - great vapor production and throat hit. I use 901 for dripping - because the wick is more accessable. I get much more kick out of 4075 attys - but I have mouthfull of yummy, non-burnt taste and tons of vapor with 901 atty.
I had some fruity juice cocktails, which I didn't like with my previous ones... just tasted so meh. Now with 901 dripping method, it's the most frequently visited juice in my collection. I thought I'd never be able to use it up - and almost about to throw-away the whole 30ml - now I'm in love with it.
Remember, SD is one of the first commercially available mod - and things do get improved over time - and I'm sure the newer mods probably would surpass SD's performance for good margin. Most of them are also cheaper than SD as well and I'd like to have them too... But SD is giving me total satisfaction at the moment, and I am planning to use this for at least a full year before I consider getting any other mods. (and so help me god.

Ergonomic? You've got to be kidding! If you're not, haven't you seen how big the Prodigy is compared to the SD? Or how big and ugly the GG? And how unshapely they are? And the JS is, well, a stick (actually, a box mod).