Hmm I don't have a Zenesis - YET. Am on the list for it. Hopefully soon. However, I have a BS A-2, A-2TM, The Line, some home made genny atties, and a few other genisis experiences. I can't say which is "better" per say... plus that is so user subjective. It depends on what you vape and the coil/wick setup you are able to make.
I would say, the genisis style atomizers, when done right are very awesome in the flavor department. Plus very simple to rebuild a coil, but a little fiddly to oxidize the wicks... I have had great experiences with them, and also not done it right, and had really bad experiences. Zen~ is eliminating some of the guess work, but I would say a new vaper could do it just fine as there are some great how to vids up. Some people hate genisis... Usually because they can't get it right.
The bulli style is pretty easy and straight fwd. But it is a little painful wrapping coils and dealing with screwdrivers. The wick has a tendency to mute the flavor also... but I have had great experiences with flavor on the A-2TM... and not as good with the A-2. I use my A-2 as a dripper, and use a SS genisis style wick in it. It is AWESOME... I use the A-2TM as designed for work vaping. Once you get the right Ω coil for your batt setup, it works pretty darn good also.
I use a Line and a A-2TM daily as my take to work atomizer setups. At home I am typically using the Line or a UFS/GGTS setup.
ETA: If you get a Bulli-Smoker A-2 style, I highly recommend getting the stainless steel one by far.